EDUCATORS’ MANUAL FOR
CARNEGIE SCIENCE CENTER’S
SCIQUEST EXHIBIT GALLERY
TABLE OF CONTENTS
TABLE OF CONTENTS
USING THIS GUIDE
EXHIBIT OVERVIEW
EXHIBIT M AP
1
2
2
3
FLIGHT
BERNOULLI “AIR”
CONVECTION CURRENTS
DRAG RACE
IN FLIGHT M OVIES
PAPER A IRPLANE TEST TUNNEL
ROLL PITCH YAW PLANE
W ALK-IN W IND TUNNEL
W ING IT
4
8
10
12
14
18
20
22
FORC ES OF NATURE
A EOLIAN LANDSCAPE
EARTHQUAKE CAFÉ
HURRICANE!
SEISMIC W AVES
TWISTER!
VOLCANO!
W HAT ’S SHAKIN’?
W HEEL OF DISASTER
W ILD W INDS
25
29
31
38
40
44
50
54
58
WAVES
A UDIO VISIBLE / VISIBLE VIBES
ECHO TUBE TUBE TUBE
EDISON PHONOGRAPH
GEORG’S W AVE
LIGHT M IXING
LIGHT SITE
PIAN-O-SCOPE
RAINBOW
RIPPLE TANK
62
65
68
70
75
77
81
84
86
89
92
95
99
102
ROCK MUSIC
SEE UV
SHADOW CATCHER
SURF’S UP
THERM -O-VISION
NATIONAL S CIENCE CONTENT S TANDARDS
BIBLIOGRAPHY
107
108
Elaine Catz
Education Division, Carnegie Science Center
November 2002
The SciQuest Gallery, support materials and web site information was made possible by a grant from
The Grable Foundation
© 2002 Carnegie Science Center. Educators and educational institutions may reproduce portions of this document for
nonprofit purposes, with proper attribution to Carnegie Science Center. No portion of the document may be used for any
commercial applications without express permission from Carnegie Science Center. Please direct inquiries to Education
Division, Carnegie Science Center, One Allegheny Avenue, Pittsburgh, PA 15212.
USING THIS GUIDE
We believe that all educators can use our exhibits to further enhance their students’
understanding of concepts studied in the classroom. We hope that the information and
activities included in this exhibit guide
EXHIBIT MODULE NAME
THEME
will help you to do just that.
Description of exhibit component.
In this guide, you will find the following
information:
•
A map of SciQuest depicting the
location of each exhibit module on the
exhibit floor.
•
A Table of Contents
•
A detailed description of each
component, formatted as shown.à
•
A table listing all exhibits and their
related National Science Education
Standards.
•
A bibliography and list of Internet
resources.
Please note: While the Carnegie Science Center
staff make every effort to keep all of the exhibits
in working order, exhibits are occasionally
removed from the building for maintenance. If
you are especially interested in studying a
specific exhibit, please call ahead to verify that it
will be fully functional.
Text Panel:
Text accompanying exhibit modules appears
in boxes bordered by double lines.
The BIG Idea:
(the main concept underlying the exhibit)
Background Information:
(what you need to know to understand this exhibit)
Try this at school:
Related hands-on science activities to try at school
appear in boxes bordered by thick lines.
Visit suggestions / questions:
Things to think about and try during your visit
appear in the boxes bordered by thin lines.
Sources:
(a list of the sources used to compile the information
above including books, magazine articles, and websites)
EXHIBIT OVERVIEW
Originally opening on November 23, 1996, the SciQuest Gallery at Carnegie Science
Center was developed with teachers in order to provide experiences that could not be
easily created in the classroom. Geared toward complementing Middle School science
curricula, SciQuest allows students to explore three theme areas:
•
The Physics of Flight
•
Forces of Nature
•
Waves
This exhibit encourages all visitors to explore these themes by learning about basic
principles, engaging in full-body experiences, and conducting multiple-outcome
experiments.
NEW AND IMPROVED!
In November 2002, SciQuest will reopen with seven brand new interactive exhibits:
Pitch Roll Yaw Plane, Volcano!, Wheel of Disaster, Edison Phonograph, Ripple Tank,
Shadow Catcher, and Visible Vibes. For more information about these and other exhibits
in the SciQuest Gallery, read on…
2
SCIQUEST GALLERY MAP
See UV
Therm-OVision
Shadow
Catcher
Light Site
Convection
Currents
Aeolian
Landscape
Wild
Winds
Earthquake Café
Seismic
Waves
Roll Pitch Yaw
Plane
Georg’s Wave
Walk-In
Wind
Tunnel
Audio Visible /
Visible Vibes
Wheel of
Disaster
Rainbow
Rock
Music
Drag Race
Bernoulli
“AIR”
What’s Shakin’?
Ripple Tank
Twister!
Paper Airplane Test
Tunnel
Light Mixing
Hurricane!
In Flight
Movies
Volcano!
Echo Tube Tube Tube
Wing It!
ENTRANCE
3
Surf’s Up
Pian-O-Scope
R
Edison
Phonograph
BERNOULLI “AIR”
FLIGHT
Three exhibits sit atop platforms shaped like the letters “A,” “I,” and “R.” Visitors use
jets of air to suspend, move or lift spheres into zones of low pressure.
< Bernoulli “A”: Two duckpin bowling balls are suspended in front of a
jet of air. When the air is activated, the balls move toward each other.
air
air
Bernoulli “I” >
A jet of air emitted
from a flexible nozzle
suspends a beach ball
in mid-air.
air
∧ Bernoulli “R”: A transparent crosssection of an airplane wing containing
vertical hollow tubes is mounted so that it
can be tilted forward and back in front of an
air jet. Ping-pong balls in the tubes rise and
fall.
Text Panel:
Hmm…
- Where is the air moving the fastest?
- Did the balls move toward or away from the fast-moving air?
What’s Going On?
Moving air has lower pressure than still air. The higher pressure of the still air can push an
object along with it as it moves to fill in the space left by the fast-moving air. Daniel Bernoulli
discovered this principle.
So What?
So…this is what creates lift and is one of the four basic forces at work in flight (Lift, Drag,
Thrust, Gravity). Birds, gliders, bats, and jets all use fast-moving air to create lift and fly!
Discover More!
- The "Bernoulli Effect" is the reason the curtain blows against your legs when you're taking a
shower! Because the rushing water lowers the air pressure inside the shower, the higher air
pressure outside pushes the curtain toward you.
- You can try the beach ball test yourself using a ping-pong ball and a blow dryer!
- Race cars have an air-foil shape on the underside of the car! The low pressure air
underneath the car helps to keep the car close to the road.
The BIG Idea:
High air pressure can push objects toward areas of lower air pressure.
Background Information:
Gas Pressure
4
BERNOULLI “AIR”
FLIGHT
When a container is filled with gas, the molecules of the gas bounce around inside of the
container. The pressure of the gas inside the container is defined to be:
Pressure =
average force of molecules bouncing against container walls
unit area
For example, a piston cylinder is filled with a certain number (N) of gas
molecules. The initial volume of the cylinder is V1 and the pressure of
the gas inside of the cylinder is P1 . Similarly, the final volume of the
cylinder is V2 and the pressure of the gas inside of the cylinder is P2 .
V1 , P1
When the piston is activated, the number of gas molecules contained by
the cylinder does not change. However, the cylinder’s volume decreases to ½ of its
original volume:
V2 = ½ V1 .
According to Boyle’s Law, at a fixed temperature, for a given amount of gas,
Pressure x Volume = a constant. This can be used to show that P1 x V1 = P2 x V2
If V2 = ½ V1
then P1 x V1 = P2 x ½ V1
so, P2 = 2 P1
In other words, when the volume containing the gas is cut in half, the pressure of the gas
inside the container increases by a factor of two.
Density
The density of the gas in the container is defined to be:
number of gas molecules in container
Density =
container volume
N
V1
N
N
2N
The final density of gas inside the cylinder is, Density2 =
=
=
= 2x
V2 1/2 V1 V1
Density1
When the volume is cut in half, the density of the gas increases by a factor of two. We
see that the pressure of the gas in a container is related to its density in the container. The
greater the density of the gas, the higher the pressure against the container’s walls.
The initial density of gas inside the cylinder is, Density1 =
Now, consider what happens when pressurized air is ejected into a large room (also filled
with air). When air is forced quickly out of a nozzle into the room, the fast-moving air
forms a cylindrical column. The fast moving molecules in the column spread apart from
one another, leaving empty space in between. Recall that the density of a gas has to do
with how many gas molecules there are in a given volume. Therefore, the density of the
air can be related to its velocity. The fast moving air is less dense than the slow-moving
air filling the room.
5
V2 , P2
BERNOULLI “AIR”
FLIGHT
All of this information is summed up by the Bernoulli Principle, which says that
as the velocity of a fluid increases, the pressure in the fluid decreases. (Note that
the term “fluid” refers to both liquids and gases, including the air that surrounds
us every day). So, at the same temperature, fast moving air has lower pressure
than slow moving air.
SLOW
MOVING
AIR
An object that is placed near the boundary between low and high-pressure areas,
will be forced into the area of lower pressure by the higher-pressure fluid.
Bernoulli A: When the air jet is turned on, the air moving between the duckpin
bowling balls has a higher velocity than the air surrounding the exhibit. The
higher air pressure on the outer sides of the balls pushes them together, toward
the area of low air pressure.
Bernoulli I:
Vertical motion: The weight of the ball is balanced by the force of
the column of air coming out of the nozzle. à
lowpressure
air
highpressure
air
highpressure
air
lowpressure
air
AIR
JET
ball
weight
force of air
ßHorizontal motion:
coming out of
nozzle
Because the air column emitted from
the nozzle is of lower pressure than
the surrounding air, the force of this surrounding highpressure air pushes the ball from all directions toward the
low-pressure air column’s central axis.
Bernoulli R: As the fast-moving, low-pressure air moves
over the tops of the hollow tubes contained by the wing
cross-section, higher pressure air below this airfoil pushes
the ping-pong balls upward to the top of the tubes. If the
airfoil were part of an actual airplane, the high-pressure air
underneath the wing would push the plane upward toward
the lower-pressure air moving over the wing. This is how
“lift” is generated.
Try this at School:
Make your own Bernoulli Blower
Materials:
- blow dryer
- plastic / foam balls
- funnel
- ping-pong ball
Procedure: Using a blow dryer and a variety of light
plastic and foam balls, see how far you can tilt the air
stream and still keep the ball suspended with the right
balance between lift and gravity.
The slow-moving air with greater pressure
pushes the ball back into the fast-moving air
stream, which has lower pressure.
If you still do not believe that faster air creates lift, try to blow a ping-pong ball out of a
funnel. Using the principles of air movement, explain why you cannot do this.
6
FAST MOVING AIR
Recall, also, that the density of the gas is associated with its pressure.
BERNOULLI “AIR”
FLIGHT
Create your own Bernoulli “A” Exhibit
Materials:
- 2 ping-pong balls
- thread (2 pieces of the same length, approximately 1-2 feet long)
- scissors
- tape
- drinking straw
Procedure:
- Using the tape sparingly, attach a piece of thread to one of the
ping-pong balls so that the ball swings on the end of the thread
like a pendulum.
- Repeat with the second ping-pong ball and piece of thread.
- Attach the loose ends of the thread (approximately 1 inch apart) to a fixed object (tabletop,
doorway, etc.) so that the ping-pong balls hang down at the same height.
- Using the drinking straw, try to force the balls apart by blowing between them. What
happens?
Visit suggestions/questions:
Bernoulli “A”: Can you point the air jet so that one of the balls moves away from the center?
Bernoulli “I”: How far can you slowly tilt the nozzle and still keep the ball in the air?
Try lightly tapping the ball from side to side as it floats in the air. What happens?
How is this part (the “I”) of the exhibit related to the “A”?
Bernoulli “R”: Can you get all four ping-pong balls to rise at once?
How are all three parts of the exhibit related to each other?
Sources:
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space Administration,
1998 (NASA EC-1998-03-002-ARC).
FoilSim Download: FoilSim was developed at the NASA Glenn Research Center in an effort to foster
hands-on, inquiry-based learning in science and math. FoilSim is interactive simulation software that
determines the airflow around various shapes of airfoils. The Airfoil View Panel is a simulated view of a
wing being tested in a wind tunnel with air moving past it from left to right. Students change the position
and shape of the wing by moving slider controls that vary the parameters of airspeed, altitude, angle of
attack, thickness and curvature of the airfoil, and size of the wing area. The software displays plots of
pressure or airspeed above and below the airfoil surface. A probe monitors air conditions (speed and
pressure) at a particular point on or close to the surface of the airfoil. The software calculates the lift of the
airfoils, allowing students to learn the factors that influence lift. The latest version of FoilSim (Version
1.4b) includes a stall model for the airfoil and a model of the Martian atmosphere for lift comparisons.
http://www.lerc.nasa.gov/WWW/K-12/FoilSim/index.html
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
7
CONVECTION CURRENTS
FLIGHT
Visitors vary the temperature of a heated rod, producing rising and sinking currents in a
tank of fluid. The currents’ shadows are projected behind the tank where they can be
easily observed.
Text Panel:
Hmm…
- Notice the patterns created near the heat bar.
- What happens to the fluid when it becomes heated?
What’s Going On?
The heater in the tank warms the fluid near it. Because warm fluid expands and takes up more
space than cold, it is less dense and rises. As the warm fluid rises through the cold, friction
creates turbulent patterns. Air acts the same.
So What?
So…air is also a fluid. Weather is affected by patterns of rising and falling air creating wind,
tornadoes, and hurricanes. Scientists study models like this to learn more.
Discover More!
- The warm water of the tropics heats the air, which rises. When the rising moist air cools, it
condenses into water vapor. This action heats the surrounding air, repeating the whole cycle
again and again, creating a hurricane hundreds of miles wide.
- While tornadoes look like they reach down from the clouds, they are formed from rising air,
pulling the funnel up.
The BIG Idea:
Heating a fluid changes its density. Relative differences in fluid density result in fluid
movement.
Background Information:
Convection is one way that heat can be transferred through a fluid (Note: the term “fluid”
is used to denote a liquid or a gas).
As a layer of a fluid is heated, it expands. Individual molecules making up the fluid
move apart from one another as they gain energy (via the heating process).
Density is a measure of mass per unit volume. The mass of an object has to do with the
number of molecules that it contains. As the molecules in a fluid spread apart, their
number per unit volume decreases. The fluid becomes less dense.
Archimedes’ Principle states that, “any body completely or partially submerged in a fluid
is buoyed up by a force equal to the weight of the fluid displaced by the body.”
This explains why, when the density of one layer of fluid is greater than the density of
another layer of the same fluid, the layer that is more dense will sink and the layer that is
less dense will float.
8
CONVECTION CURRENTS
FLIGHT
When a layer of air receives enough heat from the Earth’s surface, it expands and moves
upward. Colder, heavier air flows under it, which is then warmed, expands, and rises. As
the warm, rising air reaches higher cooler regions of the atmosphere, it cools and begins
to sink. Convection causes local breezes, winds, and thunderstorms.
Try this at School:
Cool Convection:
Make ice cubes out of colored water, then set them into a clear container (like an old aquarium)
filled with warm water. Have students make predictions and then observe the movement of the
cold, colored water. The students can see the falling and rising currents of the water by following
the trails of colored water that melt off the ice.
Visit suggestions/questions:
How could a bird use convection to make flying easier?
Where have you witnessed convection currents before?
Sources:
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
9
DRAG RACE
FLIGHT
Visitors rotate a large moveable disk that encapsulates three liquid-filled tubes. Each
tube contains a shape (a square, a circle and a teardrop) suspended in the liquid. When the
disk is rotated, the shapes rise; the aerodynamic teardrop shape wins the “race” every
time.
Text Panel:
Hmm…
- Which shape rises the fastest?
- What differences do you see in the patterns formed behind each shape?
What’s Going On?
Moving shapes have to push against any fluid they are traveling through. (Air and water are both
fluids!) This is a form of friction called ‘drag.’ Some shapes have less drag than others and win
the race – every time!
So What?
So…the design of the helmet you wear when bicycling, combined with a tucked-in body position,
reduces your drag, allowing you to move faster. This also works in skiing, trucking, and auto
racing.
Discover More!
- The winning shape is used for more than just flight. Look out the window at the USS Requin
submarine. What shapes are the conning tower and bow of the ship?
- Try experimenting with shapes in a sink or tub at home or school. Try different toy cars and
planes. Which is easiest to move?
The BIG Idea:
Drag forces act on an object that is moving through a fluid, slowing the object down.
Background Information:
There are two types of drag forces: form drag and friction
drag.
Form drag depends on the shape of the object that is
moving through a fluid.
•
The flow pattern of a fluid through which an object
moves is modified depending on the object’s shape. As
the flow pattern changes, the fluid’s velocity changes, as
does its pressure. These pressure changes result in
motion-opposing forces that act on the object.
•
Teardrop shapes have the least form drag, while
blocky shapes have the most.
Friction drag depends on the texture of the object’s surface. Friction exists when two
objects rub against one another. A rough surface will generate more friction as it moves
through a fluid than will a smooth surface.
10
DRAG RACE
FLIGHT
Try this at School:
Drag Force
(Source: Adapted from Take Flight. Museum of Science and Industry.
Chicago, 2002. http://www.msichicago.org/ed/flight/)
1
Materials:
- two-liter bottle
- blow dryer
- photocopy of a protractor
- pin
- drinking straw
- clay
- pearly-opalescent shampoo or liquid hand soap
2
3
Procedure:
- Cut the ends off the two-liter bottle to make a tube.
- Cut a ½” hole at the top of the tube. Put the pin through the middle of
4
a 4” section of the straw, and set this through the hole so it swings freely.
- Tape the protractor to the top of the bottle, as a measurable gauge.
- Investigate drag by making four quarter-sized balls of clay and making
them into the following shapes: round, square, tear-dropped and coin-shaped.
- Attach a shape to the straw and place in wind tunnel.
- Blow air through the end of the tube with the blow dryer. The amount the straw moves against
the protractor is the amount of drag created. An object with little or no drag will not move the
straw. An object with a lot of drag will be pushed by the air and tilts the straw further.
- Measure and record the drag. Test all shapes and then remold the clay to see if you can
decrease or increase the drag.
Based on the amount of drag of each shape, predict how the air moves around each object. Try
the following drag test and predict what patterns will look like based on drag measurements.
- Create a pearlized-fluid by mixing one tablespoon of a pearly-opalescent shampoo or liquid
hand soap per cup of water.
- Pour the fluid into a flat-bottomed metal or opaque-plastic pan so that the fluid barely covers
the shapes.
- Drag each shape through the fluid.
- Record the patterns seen behind each shape. What shapes have a smooth flow around
them? Which shapes have the most turbulence?
- Write a description of the patterns and relate these to the amount of drag measured in the
wind tunnel.
Challenge your students -–who can make the most aerodynamic shape?
Visit suggestions/questions:
Look out the window at the submarine.
Locate the conning tower.
Imagine that you are in the sky, looking down
at the submarine. What shape is the conning
tower from above? Why would the submarine
be designed this way?
Sources:
Cooney, Dr. Tim and Dr. Jody Stone. “Energy and Transportation: Middle School Module 3, An
Interdisciplinary Module for Energy Education.” Energy Education Curriculum Project. Center for Energy
and Environmental Education, University of Northern Iowa. Cedar Falls, Iowa. 1995.
http://www.earth.uni.edu/EECP/mid/mod3_sc.html
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space Administration,
1998 (NASA EC-1998-03-002-ARC)
11
IN FLIGHT MOVIES
FLIGHT
Visitors view artifacts and video clips allowing them to compare the structures of flying
and non-flying mammals, birds, insects, and seedpods.
Text Panel:
Hmm…
- Which bones of a bat’s hand have been adapted to make wings?
- What do you notice about how the edges of the bird wings differ?
- Which of these insects & seeds do you think can fly?
What’s Going On?
This collection of objects and video clips shows the many ways flight occurs in nature. You can
compare the adaptations that allow –or prevent – things from flying as you look at the animal
bones, seeds, and insects.
So What?
So…we have adapted some of these techniques for our mechanical flight. Landing gear, rudders,
wings, even parachutes have their basis in biological flight. We’re just happy not to have to flap!
Discover More!
- A flight feather on a bird’s wing must be a smooth surface for air flow. Each strand (barb)
has tiny hooks that keep them locked together smoothly. A bird preens to zip the barbs
together.
- A bird uses 15 times more energy to fly than to sit still. But once in flight, they can double
their speed without much of an increase in energy use.
Encased in the table are the following artifacts:
•
Bones: human arm, bat wing, pigeon wing
•
Plant Seeds (dispersion method): Basswood (flying: glider), Sedge (non-flying:
water), Maple (flying: winged), Cocklebur (non-flying: mammals), Milkweed (flying:
plumed)
•
Insects: Thorny Hopper, Giant Cicada, Dragonfly
•
Wings: Mallard, Bat, Hawk, Ruffed Grouse
The BIG Idea:
Some plants and animals have characteristics that allow them to travel via air.
Background Information:
Some animals have developed adaptations that enable them to fly. Different animals
have different adaptations that allow them to achieve the same result.
Bats and birds have wings, but they are each formed by a different part of the animals’
arms. Bat wings are formed from modified hand bones, while bird wings are modified
forelimbs.
The shape and size of a bird’s wings are adapted to its flight style. Small birds most
often exhibit flapping flight. These birds flap their wings continuously when they are in
the air. Ground dwelling birds have rounded, short wings that deliver short bursts of
12
IN FLIGHT MOVIES
FLIGHT
powerful flight. Large birds that glide have long thin wings, used to take several strong
strokes before gliding. The length of the glide depends on air and wind conditions. Birds
that soar on rising currents of air tend to have long, broad wings that they use to generate
lift. Birds that fly the fastest have sharply tapered wings.
Humans have adapted some of these techniques to create a variety of flying machines.
Try this at School:
Nature’s Helicopters
Collect maple seeds, then test them to find the best flyers. Add a dab of white-out
to each end of a seed to help see the pattern of flight. Where is the center
of rotation? Make tiny cuts to remove parts of the seeds, then test the flight.
How much and what parts of the seed must remain in order to spin?
Make maple seeds out of oak tag. Bend them slightly to make an
airfoil (a plane’s control surface that provides lift, e.g. wing) and weight
one end with a paper clip. Note the different flight paths made with different shapes.
(To spiral or spin, air must be pushing in opposite directions on the two (or opposite) ends of the
seed.)
Visit suggestions/questions:
Compare and contrast the bones of the human arm, bat wing and pigeon wing.
What types of adaptations have plants developed in order to disperse their seeds?
Compare the structures and functions of the wings of the insects, birds, and bat. What do you
think would be the advantages and disadvantages of each type of wing?
Sources:
“Flapping Wings.” Adaptive Aerofoils. Updated 05/28/02. http://www.nurseminerva.co.uk/adapt/flap1.htm
“Flight Mechanics.” The Bird Site.” The Natural History Museum of Los Angeles County Foundation.
http://www.nhm.org/birds/guide/pg018.html
Harris, Tom. “How Bats Work.” How Stuff Works. Howstuffworks, Inc. 2002.
http://www.howstuffworks.com/bat.htm.
Legg, Gerald and David Salariya. The X-Ray Picture Book of Amazing Animals. NY: Franklin Watts,
1993.
Mills, Jonathan W. “Exploring Science and Design with a Maple Seed.” The Journal of Maple Seed
Science: an International Research Forum for Kids and Teachers. Vol. 1.1. 1997.
http://www.cs.indiana.edu/~jwmills/EDUCATION.NOTEBOOK/maple/maple.html
“Whirling Wonders” Science Learning Network. Science Museum of Minnesota. 1996.
http://www.sci.mus.mn.us/sln/tf/w/whirlingwonders/whirlingwonders.html
13
PAPER AIRPLANE TEST TUNNEL
FLIGHT
Visitors make and modify a paper airplane and test it in a small wind tunnel.
Text Panel:
Hmm…
- Is the plane you made stable?
- How can you adjust the wings of a stable design to make it roll?
What’s Going On?
A stable plane flies level in the tunnel because of the even flow of air over the symmetrical wings.
Bending the backs of the wings (the ‘ailerons’) changes the even air flow and ‘rolls’ the plane left
or right.
So What?
So…engineers do the same thing you’re doing when they test model planes in wind tunnels. They
can test designs without risking lives or expensive equipment by using models first.
Discover More!
- Scientists study birds in wind tunnels, too. By videotaping the movements, they can see how
birds adjust their bodies when they fly. This helps engineers design better planes.
- Wind tunnels are also used in designing cars and trucks. Researchers can see how
aerodynamic the vehicle is by testing a small model. Slight changes mean big savings with
better gas mileage.
The BIG Idea:
Changing the physical characteristics of a plane affects its path of flight.
z
Background Information:
Changing the shape and position of a plane’s wings and tail
changes the way that it flies through the air.
y
pitch
yaw
Wings: By bending the rear edge (aileron)
of one of a plane’s wings up and the
rudder
other wing’s rear edge down, the
plane can be made to roll.
ailerons
wing
tail
elevators
roll
wing
Tail:
•
Bending the vertical portion of the tail (rudder) from
side to side controls the yaw, causing the plane to
turn toward the left or right.
•
Bending the rear edges of the horizontal parts of the tail (elevators) up or down
controls the pitch of the plane, tilting the nose up or down.
14
x
PAPER AIRPLANE TEST TUNNEL
FLIGHT
Try this at School:
Controlling Flight: Rudders, Ailerons, and Elevators
(Source: United States Air Force Museum. Wright-Patterson AFB. OH.
http://www.wpafb.af.mil/museum/edu/soar2g.htm)
Grade Level: 5-6
Time Required: Preparation: 1 hour, Activity: 1 hour
Objectives: Students will construct paper gliders and conduct a series of test flights to discover
how the rudder, elevators and ailerons affect flight. Students will measure distances flown and
use a stopwatch to determine time aloft for each glider flight.
Background
The rudder on the vertical fin steers the plane right or left. This is referred to as yaw. An elevator
points the nose of the plane up or down. This is the pitch of the plane. Ailerons help to keep the
plane steady and assist in tilting it while making a turn so that the wing on one side is lower than
the wing on the other side. This is referred to as roll.
Materials:
Each student will need:
- glider pattern
- straw
- scissors
The class will need:
- stopwatch
- tape measure (either
- heavyweight paper
- tape
- paper clip
standard or metric)
Note: Safety Instructions: Do not fly paper gliders directly at another person because the pointed tip could
cause injury. Use caution when flying the paper airplanes. Create a single direction flight zone. Be sure that
students stop flying their airplanes when other students are retrieving airplanes that have already landed.
Procedure
Explain to the class the function of the rudder, ailerons and elevators.
Activity
- Cut out the three shapes from the pattern. Cut the slits in the wings and fin, but do not fold
them back.
- Fold the wing in half along the center dotted line. Fold each wing back along the second
dotted lines. Tape the straw on top of the wing so that it sits on top of the folds. The folded
section underneath the straw will assist in launching the glider.
- Tape the tail to the end of the straw so that the end of the straw is lined up with the center of
the tail.
- Cut a slit at the top of the straw at the tail end. Insert the fin vertically into the slit and tape it
into place.
- Attach a paper clip to the nose.
- Test the glider in a large, indoor area (such as a gymnasium). At one end of the gym, put a
piece of masking tape on the floor to designate where the student will stand to launch the
glider. For the first flight, leave the rudder, ailerons and elevator flat.
- Measure and record how far the glider flew, the distance it flew, how straight it flew, and the
length of time the glider was aloft. Record results on the Recording Sheet.
- Now it is time to discover how the rudder, ailerons and elevator can affect the flight of the
glider. First, students will predict what affect each change will have on the glider. Then,
changing only one variable at a time, students will test fly the glider and record results.
- Record results.
Assessment/Evaluation: Students will write a paragraph explaining observations made during the
various test flights.
15
PAPER AIRPLANE TEST TUNNEL
FLIGHT
Extensions
- Create a graph comparing the results of the glider's time aloft when the elevators are flat as
opposed to bent. Calculate a class average.
- Write a creative story about a flight where the rudder, ailerons and elevators were frozen.
What would happen?
- Have a contest to determine which glider stays aloft the longest, flies the farthest or is the
most accurate.
- Put a master copy of the glider on the overhead projector and have students measure and
draw their own pieces to be cut out.
Result Recording Sheet
Time
Aloft
Distance
Rudder Folded Left
Rudder Folded Right
Elevator Folded Up
Elevator Folded Down
Ailerons Folded Up
Ailerons Folded Down
One Aileron Folded Up,
One Folded Down
Glider Pattern
16
Flown Direction of
Flight
Straight, Left, Right
Observations
PAPER AIRPLANE TEST TUNNEL
FLIGHT
Visit suggestions/questions:
Follow the directions on the table and make a paper airplane.
What happens if you make a plane and bend one wing up and the other down?
Try manipulating a model plane’s control surfaces at the Roll Pitch Yaw Plane.
Sources:
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space Administration,
1998 (NASA EC-1998-03-002-ARC).
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
17
ROLL PITCH YAW PLANE
FLIGHT
Visitors steer a model plane as it “flies” in a wind tunnel, by controlling the rudder,
elevators, and ailerons.
Text Panel:
Hmm…
- What happens when you adjust each control?
- How can you make the plane roll left or right?
What’s Going On?
Fast moving air over a plane creates lift, keeping the plane in the air. Moveable surfaces on an
airplane’s wings and tail allow a pilot to maneuver the plane by changing the airflow around it.
So What?
So…without being able to control the airflow around the plane, pilots would not be able to steer.
Discover More!
- Ailerons on the wings control roll. The two ailerons move in opposite directions – up and
down. This decreases lift on one wing while increasing it on another, causing the airplane to
roll left or right.
- The elevator on the tail controls pitch. The elevator tilts up or down. This decreases or
increases the lift on the tail, which tilts the nose of the airplane up or down.
- The rudder on the tail controls yaw. The rudder swivels from side to side, which turns the
plane in a left or right direction.
The BIG Idea: Pilots are able to control their planes by manipulating moveable parts
(control surfaces) located on the tail and wings.
z
y
Background Information:
yaw
The location of any object can be defined by its coordinates with respect to
three principal axes x, y and z. These axes are mutually perpendicular (at right
angles to each other). The orientation of the object can be defined by its
angles of rotation with respect to the three principal axes.
•
The object’s roll is defined to be its rotation about the x-axis.
•
The object’s pitch is defined to be its rotation about the y-axis.
•
The object’s yaw is defined to be its rotation about the z-axis.
A pilot is able to regulate a plane’s orientation in space by controlling adjustable
sections of the plane’s wings and tail.
•
The rudder is found on the vertical portion of
the tail. It helps the pilot to control yaw rotation.
•
The elevators are found on the horizontal
rudder
portions of the tail. They help the pilot to control
tail
the pitch of the plane.
•
The ailerons are found on the rear edges of the
wings. Moving the ailerons helps the pilot to
elevators
control the roll of the plane.
18
pitch
roll
x
wing
ailerons
wing
ROLL PITCH YAW PLANE
FLIGHT
Try this at School:
THE ROLL, PITCH AND YAW GAME
(Source: http://www.sln.org/pieces/cych/apollo%2010/students/activities/offline/roll.html)
Note: to view animated instructions, see the web site listed above.
This activity is only for brave teachers! But if you can carry it off - it's great fun. It's also useful for
lessons on flight!
Stand in front of the class with your arms out like an
aeroplane. Explain that you are going to show the
children how to "Roll, Pitch and Yaw"!
Get the whole class to mirror
you - first you are going to teach
them how to PITCH.
Put your head down to your
knees without bending them, still
keeping your arms out like an aeroplane...
Tell them Pitch is easy to remember because of being "pitched forwards"
or "pitchfork" etc... Do the same in the opposite direction.
Next show them how to ROLL. To ROLL just lower your right hand
down to your thigh following it with your head and lifting your (straight)
left arm in the air.
Lastly - you've guessed it, you are going to
show them how to YAW! To YAW – keep
your hands out and turn you whole upper
body from the waist.
Once you have practiced all three a couple of times – get them to do it.
The position you are in is called "attitude" – if someone gets it wrong –
you could tell them they've got a bad "attitude.”
Visit suggestions/questions:
Experiment with the plane’s controls.
Try changing one control surface (aileron, rudder, elevator) at a time and then two at a time.
What would you need to do to steer the plane down and to the left? Up and to the right?
Try making your own plane at the Paper Airplane Test Tunnel.
Sources:
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space
Administration, 1998 (NASA EC-1998-03-002-ARC).
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
19
WALK-IN WIND TUNNEL
FLIGHT
Visitors put on foam wings and step inside a wind tunnel to discover how to create
maximum lift.
Text Panel:
Hmm…
- If you were a bird, what would it feel like to fly?
- Tilt the wings. In what position do you feel the most or least resistance?
What’s Going On?
A wing is shaped to fly very easily – air flows faster over the curved top and creates low pressure,
lifting the wing – and your arm. Enough lift on the right-sized wing is what makes a plane or a
bird fly.
So What?
So…subtle differences in the design and position of wings greatly affects their ability to fly.
While pilots work at keeping the wings at the right angle, you can relax and try to get those
peanut packets open.
Discover More!
- In flight, lift is important, but you don’t want to just keep going up, up and up! Controlling
and adjusting the angle of wings allows a pilot or a bird to reach a certain altitude and stay
there.
- The tilt of the wings is called the “angle of attack.” If they are back too steep, you stall. If
they are too far forward, you dive.
The BIG Idea:
Airplane wings are shaped such that lift is generated as the plane moves through the air.
Background Information:
Four forces act on an object in flight.
Lift
•
Lift is the force that carries a wing (and whatever is
connected to it) up into the air. As a wing moves
through the air, fast moving air over the top of
Thrust
the wing has lower pressure than the air
Drag
underneath. The higher pressure of the air
underneath pushes the wing up as it moves into the space
created by the low pressure. The ‘angle of attack’ or tilt of the
Weight
wing, comes into play as the tilted wing rides on the air
molecules pushing up as they flow underneath.
•
Weight is the result of gravity pulling an object toward the earth.
•
Thrust is the force that propels an object forward. This may be generated by the
exhaust exiting jet engines, by air moving through spinning propellers, or by flapping
wings. The amount of energy used to create enough thrust varies with the type of flight
and size of the object being lifted.
•
Drag is the force that slows an object’s motion as it moves through a fluid (liquid or
gas). Drag is a type of friction that can be used to slow a flying object, allowing it to
descend or land. There are two types of drag: form and friction. Streamlining the
20
WALK-IN WIND TUNNEL
FLIGHT
shape of a flying object’s body will reduce form drag by decreasing motion-opposing
pressure changes surrounding the object. Smoothing the surface of the flying object
will reduce friction drag by allowing the molecules to move smoothly over the outer
“skin.” The amount of energy needed to move an object depends on the amount of
drag that must be overcome.
Try this at School:
Need a Lift? Design and test a number of airfoils.
An airfoil is a control surface on an airplane or other vehicle that acts on
air to provide lift and stability.
Materials:
- 8½” x 11” sheets of paper
- tape
- scissors
- pencils
Procedure:
- Cut an 8½” x 11” sheet of paper lengthwise into 2 strips.
- Bend the strip back on itself and tape the ends together.
- Bend and crease the loop to make an airfoil shape.
- Thread the pencil through the side of the airfoil and blow across the top of the airfoil.
- Try semi-circular and triangular shapes. Which wing shape creates the most lift?
Visit suggestions/questions:
What happens when you tilt your wings at a steep angle while in the tunnel?
Sources:
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space
Administration, 1998 (NASA EC-1998-03-002-ARC).
FoilSim Download: FoilSim was developed at the NASA Glenn Research Center in an effort to foster
hands-on, inquiry-based learning in science and math. FoilSim is interactive simulation software that
determines the airflow around various shapes of airfoils. The Airfoil View Panel is a simulated view of a
wing being tested in a wind tunnel with air moving past it from left to right. Students change the position
and shape of the wing by moving slider controls that vary the parameters of airspeed, altitude, angle of
attack, thickness and curvature of the airfoil, and size of the wing area. The software displays plots of
pressure or airspeed above and below the airfoil surface. A probe monitors air conditions (speed and
pressure) at a particular point on or close to the surface of the airfoil. The software calculates the lift of the
airfoils, allowing students to learn the factors that influence lift. The latest version of FoilSim (Version
1.4b) includes a stall model for the airfoil and a model of the Martian atmosphere for lift comparisons.
http://www.lerc.nasa.gov/WWW/K-12/FoilSim/index.html
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
21
WING IT
FLIGHT
Visitors run their arms along a segment of a special railing to replicate the figure-eight
motion of a bird's wings in flight.
Text Panel:
Hmm…
- What does it feel like to move your arms like a bird?
- Does this remind you of an activity you do in the water?
What’s Going On?
Birds don’t simply flap their wings up and down. Like your arms as you move along this railing,
birds flap their wings in a figure-eight. This moves enough air over their wings to create lift and
thrust.
So What?
So…since planes can’t flap their wings like a bird, engineers had to figure out a different way to
move enough air for lift and provide separate thrust. They devised propellers, rockets, and fixed
wings.
Discover More!
- Biologists believe geese fly in a “V” formation to make flying easier. Birds in the back use
less energy because of the air currents created by the formation. They even take turns being
at the front of the line to give each other a break.
- Hummingbirds beat their wings 80 times a second!
The BIG Idea:
Birds move their wings in such a way as to generate lift and thrust.
Background Information:
A flying bird is able to adjust the shape and position of its wings in order to generate lift,
change direction, and land. In particular, the flight feathers – both primary and
secondary, contribute to the bird’s maneuvers in
the air. Each of a bird’s flight feathers is
connected to a muscle, allowing the bird to modify
secondary
its position individually.
flight feathers
A bird generates lift using its wings. Faster air
moving over the top of the wings creates areas of
low air pressure above the bird. The bird is then
pushed upward by the higher-pressure air beneath
it.
primary flight
feathers
Birds move their wings in two ways during
flapping flight: the portion of the wings that are close to the body move up and down,
while the tips of the wings move in a circular, propeller-like motion. Most birds are able
to articulate their wings at the shoulder, elbow and wrist. (An exception is the
hummingbird, which is only able to articulate its wings at the shoulder.)
22
WING IT
FLIGHT
The downstroke is the portion of flight that gives a bird power. During the downstroke,
the primary feathers overlap each other so that air cannot get through. The tips of the
primary feathers are bent upward and are twisted at an angle to the wing, drawing air up
and back.
During the upstroke, the primary flight feathers separate in order to allow air to slip
through the wings, minimizing drag forces. The wing tips move up and back against the
air and the part of the wings nearest the shoulders are responsible for providing lift.
The angle of attack is the angle at which the bird’s wings face the oncoming air. When
the angle is too steep, the bird is in danger of stalling. To prevent this, the bird is able to
open and close small slots between sections of feathers on its wings. This results in
changes in the speed of the air moving over the wings, helping to reinstate smooth flight.
Try this at School:
Make a flip book.
The following page contains 12 frames, each depicting a portion of a bird’s flight sequence.
- Duplicate the page and cut the individual frames apart.
- Create a book by stacking the pictures in order by number. For best results, use two to three
copies of each picture: 1-1-1, 2-2-2, 3-3-3…12-12-12.
- Staple the book together in the upper left-hand corner (near the numbers).
- Flip through the book with your thumb to watch the movement of the bird’s wings.
- Follow the tip of the bird’s wing through the flight sequence. What shape does the bird’s wing
trace out?
Visit suggestions/questions:
Was it harder to move your arms than you expected? Why or why not?
Sources:
“Birds in Motion.” Encarta Encyclopedia. CD-ROM. Microsoft Corporation. 2001.
“Flapping Wings.” Adaptive Aerofoils. Updated 05/28/02. http://www.nurseminerva.co.uk/adapt/flap1.htm
“Flight Mechanics.” The Bird Site. The Natural History Museum of Los Angeles County Foundation.
http://www.nhm.org/birds/guide/pg018.html
Legg, Gerald and David Salariya. The X-Ray Picture Book of Amazing Animals. NY: Franklin Watts,
1993.
Peterson, Roger Tory. A Field Guide to the Birds. 4th ed. Boston: Houghton Mifflin. 1980.
Peterson, Roger Tory. “What It Takes to Fly.” The Birds. Life Nature Library. Time Life Books. Time
Inc. 1970.
“Wings in Motion” Take Flight. Museum of Science and Industry. Chicago. 2002.
23
WING IT
FLIGHT
1
2
3
4
5
6
7
8
9
10
11
12
24
AEOLIAN LANDSCAPE BY NED KAHN FORCES OF NATURE
Visitors vary the direction of a blowing fan, creating dunes in a chamber filled with small
plastic flakes.
Text Panel:
Hmm…
- What wind and sand patterns do you see?
- How do the wind or sand patterns change when you alter the “wind” direction?
What’s Going On?
Plastic flakes blown by the fan simulate the interaction of wind on sand or snow. The particles
are dropped where the wind slows down – often behind rocks, dunes or trees. The landscape
changes the wind and the wind changes the landscape.
So What?
So…controlling movement of sand and soil is difficult. Soil erosion can be a major loss for
farmers. Methods include planting wind breaks or a winter crop to help reduce soil loss.
Discover More!
- Dunes are generally one of three types: linear are the familiar parallel lines of “waves”
made by strong, steady winds; crescents are half-moon curves; star are irregular dunes with
“arms” created by erratic winds.
- Shifting dunes on beaches and deserts can threaten communities – some dunes travel up to 50
feet per year as sand from the back tumbles over the front crest.
The BIG Idea:
When the ground is primarily made up of loose sand or soil, wind can play a major part
in shaping the landscape.
Background Information:
The term aeolian (or eolian) means “caused, transmitted, or carried, by the wind.” An
aeolian landscape is a landscape that is shaped by the wind.
In order for the wind to shape the landscape, the ground must be primarily made up of a
large amount of loose sediment– sand and soil. There must be very little vegetation
blocking the flow of the particles.
The wind shapes the land in different ways. It may erode (wear away) rock and stone
that block its path, carrying away fine particles and depositing them elsewhere. The wind
may also move large grains of sand slightly above the ground such that they skip across
the surface in a process called “saltation.” Saltating grains may push along larger grains
and the slow continuous movement that results is known as “surface creep.”
When saltating grains are blocked (e.g. by vegetation or large rocks) then a sloped mound
of sand or soil, known as a sand dune, may begin to form. Sand dunes are found in the
desert, in coastal regions and along shorelines. The sand grains move up the front slope
(the side of the dune that faces the oncoming wind, called the “windward” side) by
saltation. The particles then spill over the top as a landslide, down the opposite side of
25
AEOLIAN LANDSCAPE BY NED KAHN FORCES OF NATURE
the dune, called the “leeward” side. The leeward side is also called the “slipface,”
because it is the side that the moving sand particles slip down.
The most common types of sand dunes are crescents, linear, and star.
wind direction
windward
side
slipface
leeward
side
SAND DUNE
(crescent)
path of sand
particles
direction of
dune movement
Crescent-shaped dunes are the most common type of sand dune on Earth. A crescent
dune is wider than it is long with a gentle slope on
windward
leeward side
the windward side and a steep slope on the
side (gentle
(steep
slope)
leeward side. The dune becomes concave on its
slope)
dune
leeward side. Crescent dunes form in places
top view
direction
where the wind constantly blows from one
wind
direction
direction.
Crescent-shaped Dune
Linear (or longitudinal) dunes also result from
winds that blow only in one
direction. Linear dunes tend to be
wind
elongated in the direction of the
direction
wind and have similar slopes
running down both sides. While
this type of dune may occur as an
ridge runs horizontally along dune
dune
direction
Three Linear Dunes
isolated ridge, linear dunes are more often
formed in parallel groups.
slipface
dune
direction
slipface
Star-shaped dunes form in places where the
wind originates in many directions. They
have multiple slipfaces on arms radiating
from a high center. Star-shaped dunes tend
Star Dune
to grow such that they become taller, rather
than longer.
Dunes may be simple, compound or complex. A simple dune has a minimum number of
slipfaces that define the dune’s type. A compound dune is a large dune on which smaller,
similar dunes are superimposed (similar slipface orientation, type). A complex dune is a
large dune formed from smaller dunes of two or more types.
26
AEOLIAN LANDSCAPE BY NED KAHN FORCES OF NATURE
Dunes that are not stabilized by vegetation or other obstructions may migrate, moving
across the land damaging homes, roads and agricultural areas. To prevent dune
migration, vegetation can be planted, ground moisture can be increased and physical
barriers can be constructed.
Try this at School:
Sand Dune Erosion in a Box Top
(Source: “Sand Dune Erosion in a Box Top.” Carolina Science and Math. Carolina Biological Supply
Company. 2002. http://www.carolinea.com/calendar_activities/2002/0202.asp)
Background
Sand particles, and the dunes they form, are moved by wind and water in a process called
erosion. In nature, the interacting forces of erosion can be quite complex. However, this month's
activity for elementary and middle school students demonstrates the concept and effects of
erosion simply and inexpensively using found materials. This activity meets the following national
standard for elementary and middle school earth and space science: Properties of Earth
Materials.
Materials
- A wind source (e.g., a blow dryer or air mattress inflator)
- Blue food coloring
- Red food coloring
- Sand with diverse grain sizes (1 Liter per student group)
- Tops from copier paper boxes
Preparation (instructor)
1. Divide your class into working groups of 3–4 students each.
2. For each group of students, color 250 ml of sand with 7 drops of the red food coloring and color
another 250 ml of sand with 7 drops of the blue food coloring.
3. Allow the sand to dry completely before using it. If time is limited, you can dry it in an oven. Be
sure to allow the sand to cool before giving it to your students.
4. Provide each group with 250 ml of red sand, 250 ml of blue sand, 500 ml of uncolored sand, a
box top, and a wind source (which can be shared between groups if necessary).
Caution: If you intend to use a blow dryer as your wind source, use it with the heat off and instruct
your students to do likewise.
Note: This activity usually results in fine sand landing outside of the box top. If weather permits,
perform the experiment outdoors to reduce the cleanup effort.
Procedure (students)
1. Place the copier paper box top upside down on a flat surface.
2. Cut or tear 2 corners of the box top lip at one end of the box top. Press the loose section of the
lip down flat. The other 3 sections of the lip should remain standing.
3. Create a "dune" by pouring the red sand in a straight line across the open end of the box top.
The dune should be about 8 cm wide and 2 cm deep.
4. Using the blue sand, create another dune of the same size behind and adjacent to the red one.
5. Using the uncolored sand, create 2 more dunes, each the same size as the previous ones,
behind and adjacent to the blue one.
6. Predict how the sand will be affected by a horizontal wind blowing directly into the dunes.
7. Use the wind source to create a horizontal wind blowing directly into the dunes. Start with a
fairly low wind speed and then increase it. Continue until about half the red sand has been
27
AEOLIAN LANDSCAPE BY NED KAHN FORCES OF NATURE
eroded. Note any changes in the behavior of the dunes and the particles of sand at different wind
speeds.
8. Observe the distribution of the colored sand particles. Are there any differences in the
distributions of the red and blue particles? Are there any differences in the distributions of
particles of different sizes?
Extension activities and questions
1. How does the shape of the dunes affect their erosion? Investigate by building semicircular or
serpentine model dunes and applying wind to them.
2. How do changing wind directions affect dune erosion? Find out by blowing wind across the
dunes from different directions.
3. How does water influence wind erosion of the dunes? Spray the dunes with varying amounts of
water before applying wind to them. Note: The food dyes are water-soluble and may separate
from the colored sands. Take precautions to avoid stains.
4. How do plants influence dune erosion? Use dried lichens to model shrubs on your dunes.
Apply wind to the dunes and see what effect the shrubs have on erosion.
5. Do plants act only as barriers at the surface, or do their roots also affect dune erosion? Look
into this question by partially burying a shrub in a dune and setting another shrub on the surface.
Apply wind to the dune and then compare the erosion around the 2 shrubs to see if there is a
difference.
Visit suggestions/questions:
Experiment with the Aeolian Landscape exhibit.
Turn the wheel to rotate the fan.
What types of dunes can you form?
Look carefully at the small shiny particles inside the chamber. What are they? Hint: What is a
sandblaster used for?
Sources:
The American Heritage Dictionary of the English Language. 4th ed. Houghton Mifflin. 2000.
“Desert.” Microsoft  Encarta Online Encyclopedia. Microsoft Corporation. 2002. (July 26, 2002).
http://encarta.msn.com
“Deserts: Geology and Resources, Online Edition.” United States Geological Survey. (7/26/02).
http://pubs.usgs.gov/gip/deserts/
“Dune.” Encyclopedia.com. Tucows Inc.(7/26/02).
http://encyclopedia.com/printable.asp?url=/ssi/d1/dune.html
“Geoindicator: Dune formation and reactivation.” The U.S. Global Change Research Information Office.
(7/26/02). http://www.gcrio.org/geo/dune.html
“How Much Sand is There?” Great Sand Dunes National Monument and Preserve. (7/26/02).
http://www.nps.gov/grsa/how%20much%20sand.htm
28
EARTHQUAKE CAFÉ
FORCES OF NATURE
Four visitors sit in a café booth and select one of three actual earthquakes from a menu.
The booth shakes, recreating the earthquake based on its original seismic readings.
Text Panel:
Hmm…
- What differences do you feel between the earthquakes?
- What do you think it would be like to be in a real quake?
What’s Going On?
This simulator recreates three actual earthquakes, based on the seismic reading recorded from
the originals.
So What?
So…each person in an earthquake will experience it a bit differently, depending on what kind of a
building they are in, whether they are sitting or standing, or what’s under the ground they are on.
Discover More!
- The New Zealand quake here is also on the “Seismic Wave” computer exhibit. Once you’ve
experienced this tremor, see how those shock waves traveled through and over the Earth.
- The length of time of each quake has been doubled in this simulation. People who were in
these actual quakes said they felt the tremor much longer than they actually were, so we’ve
made them longer for you to experience.
The BIG Idea: Different earthquakes have different seismic wave patterns.
Background Information:
The motion of an earthquake is described as follows:
•
Peak velocity: how fast the ground is moving
•
Peak acceleration: how quickly the speed of the ground is changing
•
Frequency: how often the ground vibrates as the released energy moves through it per
some amount of time
•
Duration: how long the shaking lasts
Three factors that primarily determine what you feel in an earthquake are:
•
Magnitude: You feel more intense shaking from a big earthquake than from a small
one; big earthquakes release their energy over a larger area and for a longer period of
time. In most cases, only 10-15 seconds of shaking originating from the part of the
fault nearest you will be strong.
•
Distance from the fault: Earthquake waves die off as they travel through the Earth so
shaking becomes less intense farther from the fault.
•
Local soil conditions: Certain soils greatly amplify the shaking in an earthquake.
Seismic waves travel at different speeds in different types of rocks. Passing from
rock to soil, the waves slow down but get bigger. A soft, loose soil will shake more
intensely than hard rock at the same distance from the same earthquake. The looser
and thicker the soil is, the greater the amplification will be.
29
EARTHQUAKE CAFÉ
FORCES OF NATURE
Try this at School:
Liquefaction: a phenomenon that occurs when “solid” ground becomes saturated with water and
behaves like a viscous liquid.
- Fill two large clear containers half full of sand.
- Slowly add water to one of the containers until the water is just below the surface of the sand.
- Wait a few minutes for everything to settle, then gently set a rock
of equal size and weight on top of the sand in each container.
- As you vibrate the containers, observe what happens to the rocks. You
may want to make a variety of surfaces to try – gravel, aquarium rock,
sand, etc.
This change to a normally solid surface is what caused the greatest areas of damage in the 1989
San Francisco earthquake. Neighborhoods built on looser landfill became the weakest and
suffered the most property loss.
Visit suggestions/questions:
Time the quakes in the Earthquake Café. To make people feel that they really experience a
quake, the exhibit designers had to double the length of time the actual earthquakes took.
Select the New Zealand earthquake. How many aftershocks did you feel? The New Zealand
selection is also in the ‘Seismic Waves’ exhibit. Look at the seismograph readings displayed for
this quake at Seismic Waves. Do the readings represent the earthquake that you experienced?
Sources:
“Earthquake Hazards Program.” United States Geological Survey. http://earthquake.usgs.gov/
Glasscoe, Maggi. “Earthquakes.” The Southern California Integrated GPS Network Education Module.
Updated 8/14/98. http://scign.jpl.nasa.gov/learn/eq.htm
“Ground Liquefaction.” http://www.nd.edu/~quake/education/liquefaction/
“Liquefaction.” Faultline. Exploratorium. CA. 1999.
http://www.exploratorium.edu/faultline/activities/liquefaction_activity.html
Pendick, Daniel. “The Restless Planet: Earthquakes.” Savage Earth. PBS Online.
http://www.thirteen.org/savageearth/earthquakes/index.html
30
HURRICANE
FORCES OF NATURE
Visitors spin a 42”-diameter disk of pearlized fluid, creating a hurricane-like vortex.
Text Panel:
Hmm…
- What happens when you spin and then stop the disk?
- Where is the fluid moving the fastest? The slowest?
What’s Going On?
A simple spin sets a lot of complex forces to work creating spiraling patterns. Friction between
the liquid, the glass, and the varying speed of the fluid in the center and the edge combine to
create currents similar to a hurricane.
So What?
So…weather patterns are similar to this example of fluid dynamics. The friction of air against
the sea and the spinning of the Earth are factors in the creation and speed of real hurricanes.
Discover More!
- Hurricanes spiral in either direction. In the northern hemisphere, they move
counterclockwise, and are reversed in the southern.
- The spin of the Earth helps create water and air currents. The energy in hurricanes is from
the warm water.
- When hurricanes move across land they slow down because their ‘fuel’ is lost. The energy
source of the warm water is gone, and the increased friction of dry land slows the wind.
The BIG Idea: Hurricanes are large, spiral-shaped storms that form over bodies of water.
Background Information:
Hurricanes are severe tropical storms whose winds exceed 74 miles per hour (mph).
From space, hurricanes look like giant pinwheels, their winds circulating around an eye
that is between 5 and 25 miles in diameter. The eye remains calm with light winds and
often a clear sky. Hurricanes may move as fast as 50 mph, and can become incredibly
destructive when they hit land, although they lose the energy from the warm ocean waters
rapidly as soon as they leave the ocean.
counter-clockwise
rotation
Eye (calm, no cloud cover)
Strongest part of the storm
surrounds eye
(Northern
Hemisphere)
(Hurricane Andrew 8/25/1992 Source: NASA: Visible
Earth
http://visibleearth.nasa.gov/cgi-bin/viewrecord?18666)
31
HURRICANE
FORCES OF NATURE
Try this at School:
Tracking a Hurricane
Suggested Level: Grades 4-6
(Source: 10th Annual National Science & Technology Week, 1993-1994.)
Background Information:
Hurricanes, one of the most destructive natural forces on Earth, are created by weather patterns.
Our atmosphere is filled with continuous patterns of activity and change: clouds, formed of water
drops and dust, move across the sky; air temperatures rise and fall; and surface winds shift
direction. This never-ending activity can be recorded because it’s observable and measurable.
The air around Earth moves constantly, stirred and mixed by rising air that’s been warmed by the
sun. Earth’s rotation increases the movement, producing winds that carry moisture and heat
around the globe, as warmer air moves into cooler areas. The warm air holds water droplets that
condense and form even larger drops as air cools, thus increasing the possibility of precipitation,
which may be in the form of rain, snow, sleet, or hail.
Hurricanes are large storms that form in warm, moist, tropical air near the Equator. During late
summer and early fall, moisture from warm ocean water begins to evaporate very rapidly. Colder
air from above moves down and pushes more warm air up. This transfer of warm air moving up
with cold air moving down begins to spiral around a central core. The movement continues until
huge
amounts
of
heated moist air are spiraling high in the atmosphere.
When winds reach 119 kilometers per hour (kph) (74 mph), the “tropical depression” becomes a
hurricane, with the most turbulent weather in the cloud wall surrounding the eye.
As long as hurricanes remain over warmed water, winds whip violent waves and dump torrents of
rain there. Hurricanes, however, have both a circular and a forward motion; winds travel
counterclockwise (in the Northern Hemisphere) around the eye in speeds up to 322 kph (200
mph); the storms move forward at approximately 24-32 kph (15-20 mph). Earth’s rotation causes
the storms to veer slightly westward, away from the Equator, and hurricanes can then occur
thousands of kilometers (miles) from their points of origin, with turbulent winds and tumultuous
rain in their paths.
Hurricanes have the potential for bringing flooding, property damage, bodily injury, and even
death. Because of the destructive force of such storms, meteorologists constantly monitor areas
where hurricanes are likely to form. These scientists use information form satellites and special
airplanes, called “Hurricane Hunters,” to help them predict the path a hurricane is most likely to
take. Such predictions, even if not always entirely accurate – an erratic storm can veer off course
or lose its force – often protect lives and property.
People living in areas where hurricanes are a possibility need to be prepared. The National
Weather Service issues information about hurricanes. A hurricane watch or advisory is issued
when meteorologists believe a hurricane may hit the area. The watch is upgraded to a hurricane
warning when immediate precautions are to be taken. People in the path of the storm may be
told to go to an area shelter, but sometimes evacuation is the only solution to minimize threat to
life. As hurricanes move over land, they lose their source of energy and consequently die.
Activity:
This activity immerses students in the process of tracking an actual hurricane, and in the
prediction process that is necessary when planning emergency evacuations. Students may work
in pairs or in small groups to (1) interpret a series of reports that track the progress of a hurricane,
(2) plot the hurricane’s progress on a map, and (3) identify locations that may need to be
evacuated. The activity has been designed to be used during two 45- to 60-minute periods, but
may also be scheduled over several days, to simulate the actual length of time documented by
hurricane tracking reports.
32
HURRICANE
FORCES OF NATURE
What You Need Per Student Pair:
- 1 hurricane tracking map
- colored pencils
Per Class:
- 1 wall map of southeast US and Caribbean, with easy-to-read latitude and longitude
lines(smaller copies of same map for pairs to use as reference)
- copies of hurricane tracking reports – 1 set for each student-pair
- small envelopes
What You Do:
- Make copies of the tracking map and the tracking reports before class starts. Cut the tracking
reports apart – you’ll be giving one to each pair of students. Place similar reports together in
an envelope and label it with the date / time shown on the report. For example, put all reports
for 09/20/89 – 3:55 p.m. in an envelope labeled 9/20 3:35 p.m.
- Begin by reviewing a few map-reading skills with the class. Ask volunteers to tell how to
determine direction, distance, etc., on a map. Practice locating a few places on the large wall
map, using longitude and latitude coordinates. Reverse the process so students have
practice reading the coordinates from the lines on the map as well.
- Share the opening information about hurricanes with the class; then ask a volunteer to write
on the chalkboard or transparency the following:
- Hurricanes moving over tropical waters gain speed and energy.
- Hurricanes moving over land begin to lose speed and energy.
- Hurricanes move over water at about 24 kph (15 mph).
- Hurricanes move over land at about 14 kph (9 mph).
- Hurricane winds generally stretch 96 kilometers (60 miles) from the eye.
- Warm bodies of water, like the Gulf Stream, can change the direction and energy of a
hurricane.
- Hurricanes in the Atlantic originate near the Equator and tend to move west.
- Divide the Class into pairs and have them find clear work areas, where they can spread out
tracking maps. Ask each pair to locate and label the Caribbean Islands, the southeastern
states of the U.S., and a few major cities in each area.
- Tell students to imagine they are meteorologists at the National Hurricane Center, where
everyone is keeping an eye on a hurricane that is forming in the Atlantic. Explain that each
student-pair will be receiving hurricane tracking reports, based on updated satellite and air
observations.
- Distribute one copy of the first report to each pair of students from the envelope labeled 9/14
12:00 noon. Explain that, using that report, each pair is to plot the location of the hurricane,
then write the time of the report on the map next to the plot location.
- Wait until every student-pair has successfully completed this first step. Explain that more
tracking reports will be coming, and students will follow the same procedure each time.
- Ask students, How do you think we might be able to figure out which way the hurricane will
move next? Explain that by using the list of facts about hurricanes, students should be able
to give and “educated guess” and predict the storm’s path. Have each pair use a colored
pencil to draw a dotted line showing the direction in which the pair thinks the hurricane will
head before the next tracking report is received.
- Continue to distribute tracking reports, every 5-10 minutes, allowing pairs time to plot and
label the location of the hurricane and predict its movement. With each successive report,
have each pair compare its prediction with the actual path of the storm.
- Explain to students that as the hurricane moves in the direction of land, they need to predict
when it may be necessary to issue an evacuation warning, suggesting to local officials that it
would be best to remove people form an area in the hurricane’s path. Remind students that
hurricanes sometimes build enough energy to carry them far inland and trigger flooding and
tornadoes before they die. Explain that most areas require twelve hours for the evacuation
process, and no fewer than six hours.
33
HURRICANE
-
-
FORCES OF NATURE
When a pair feels an evacuation is warranted, the two should issue it, specifying the following
information:
- Name of the hurricane
- Time and date of evacuation warning
- Names of meteorologists issuing the warning
- Major residential areas (cities and towns) involved
- Estimated time of hurricane’s landfall (when it will come ashore and strike)
- Potential wind speeds and rainfall estimates
Using colored pencils, the student-pair should shade the evacuation area on the hurricane
tracking map.
Read or make copies of the fictional report in the box below. If you make copies, distribute
them and then read the advisory with students.
Let each student-pair display its map and report on the success of its predictions during the
simulation at the conclusion of steps above. Then, as a group discuss the project, asking
questions like: At what point did it become difficult to track the hurricane? Why do you think
the hurricane changed direction? What areas were evacuated unnecessarily? What areas
were endangered by the hurricane but were not evacuated? How do you think people in the
hurricane watch area prepared for the storm? Do you think it was easy to get everyone in the
evacuation area to leave their homes? Why?
HURRICANE HARRY ADVISORY
NATIONAL WEATHER SERVICE
MILLY SUNSHINE – METEOROLOGIST
9:00 P.M. AST MON., SEPT. 18, 1989
Hurricane Harry is nearing the eastern tip of Caribe Island. The
government of Caribe has issued a hurricane warning for eastern Caribe
effective at 9:00 a.m. Sept. 19, 1989 Atlantic Standard Time. Harry has
been wobbling but generally moving towards the northwest at nearly
16 kilometers per hour (10 mph). All residents should proceed immediately
to designated hurricane shelters. The center of the hurricane threatens to
move over the island, bringing the full force of the storm to the island.
The slow, erratic movement is expected to continue, prolonging the heavy
rains. Residents of Caribe should be advised that landfall of the hurricane
over the next 6 hours will bring heavy rains, flooding, mud slides, and sustained winds of 177 km per hour
(110 mph). The next hurricane advisory report will be issued at 3:00 a.m.
Assessment:
As students use the hurricane-tracking activity, you may wish to track their progress. Note your
observations on a checklist. As you assess their progress, look for the following outcomes:
Specific Skills
- Student can describe the factors necessary to form a hurricane
- Students can state at what wind speed a storm officially becomes a hurricane.
- Student can plot a course on a map, using longitude and latitude.
- Student can provide evidence for decisions and predictions.
Extensions:
- Create a large tracking map, post it on a bulletin board, and have students use data from local
and national media to plot the progress of active hurricanes.
- Encourage students to research information about historic hurricanes that hit the U.S.
mainland in the past 100 years. How far up the East coast of the U.S. have hurricanes hit?
How do you think they get the energy to get that far from the Equator, where they were
formed?
- Invite a weather forecaster or meteorologist to speak to your students about hurricanes and
other giant storms that are tracked. Before the visit have students make a list of questions.
34
HURRICANE
FORCES OF NATURE
Hurricane Tracking Reports
9/14/89 – 12:00 noon
Tropical Storm Center located 13.3N latitude, 47.6W
longitude
Winds 80 kilometers per hour (kph) (50 mph)
Flooding and heavy rains to be expected
9/20/89 – 3:35 p.m.
Hurricane Center located 24N latitude, 70W longitude
Winds sustained at 90 kph (56 mph) with gusts of 105
kph (65 mph)
9/20/89 – 3:59 p.m.
Hurricane Center located 25N latitude, 71W longitude
Winds sustained at 90 kph (56 mph) with gusts of 105
kph (65 mph)
9/15/89 – 6:00 a.m.
Tropical Storm Center located 14.0N latitude, 51.9W
longitude
Winds 110 kph (68 mph)
High tidal waves and flooding expected
9/20/89 – 10:06 p.m.
Hurricane Center located 27N latitude, 73W longitude
Winds sustained at 90 kph (56 mph) with gusts to 110
kph (68 mph)
9/16/89 – 12:00 noon
Hurricane Center located 15.4N latitude, 58.4W
longitude
Winds sustained at 120 kph (75 mph) with gusts to
140 kph (87 mph)
9/21/89 – 3:39 a.m.
Hurricane Center located 28N latitude, 74W longitude
Winds sustained at 95 kph (59 mph) with gusts of 110
kph (68 mph)
9/17/89 – 6:00 p.m.
Hurricane Center located 16.9N latitude, 63.5W
longitude
Winds 125 kph (78 mph)
Flooding 2-2.4 m (6-8 ft) above normal
Rainfall of 15-26 cm (6-10 in.) in path of hurricane
9/21/89 – 10:40 a.m.
Hurricane Center located 29N latitude, 76W longitude
Winds sustained at 95 kph (59 mph) with gusts of 110
kph (68 mph)
Storm surge flooding 2.4 – 3.6 m (8-12 ft) above
normal tide
Rainfall amounts up to 26 cm (10 in.) in path of storm
9/18/89 – 3:23 a.m.
Hurricane Center located 17N latitude, 64W longitude
Winds 120 kph (75 mph) with gusts to 140 kph (87
mph)
Flooding of 2.4 m (8 ft) above normal
Rainfall amounts up to 26 cm (10 in.) in path of
hurricane
9/21/89 – 7:25 p.m.
Hurricane Center located 30N latitude, 78W longitude
Winds sustained at 100 kph (62 mph) with gusts of
130 kph (81 mph)
Storm surge flooding of 3-5 m (10-15 ft) above normal
tide
Rainfall amounts of up to 26 cm (10 in.) in path of
storm
9/18/89 – 10:18 p.m.
Hurricane Center located 19N latitude, 67W longitude
Maximum winds of 100 kph (62 mph) with gusts of
120 kph (75 mph)
Storm surge flooding of 1.2-2m (4-6 ft) above tide
levels
Rainfall amounts of 26 cm (10 in.) in path of hurricane
9/21/89 – 9:58 p.m.
Hurricane Center located 31N latitude, 78W longitude
Winds sustained at 120 kph (75 mph) with gusts of
140 kph (87 mph)
Storm surge flooding of 4-5 m (12-17 ft) above normal
tides
Rainfall amounts of up to 26 cm (10 in.) in path of
storm
9/19/89 – 3:45 a.m.
Hurricane Center located 20N latitude, 67W longitude
Maximum winds sustained at 95 kph (59 mph) with
gusts of 110 kph (68 mph)
Storm surge flooding of 1.2-2 m (4-6 ft) above tide
levels
Rainfall amounts to 26 cm (10 in.) in path of hurricane
9/22/89 – 3:42 a.m.
Hurricane Center located 32N latitude, 80W longitude
Winds sustained at 60 kph (37 mph) with gusts of 75
kph (47 mph)
Storm surge flooding 4-5 m (12-17 ft) above normal
tides
Rainfall amounts of up to 26 cm (10 in.) in path of
storm
9/19/89 – 4:55 p.m.
Hurricane Center located 18N latitude, 66W longitude
Winds sustained at 110 kph (68 mph) with gusts of
120 kph (75 mph)
Flooding of 1.2-2m (4-6 ft) above normal
Rainfall amounts to 38 cm (15 in.) in path of hurricane
(Source: Hurricanes Reproducible Page: 10th Annual National Science & Technology Week, 1993-1994. p.39.)
35
HURRICANE
FORCES OF NATURE
(Source: Hurricanes Reproducible Page: 10th Annual National Science & Technology Week, 1993-1994. p.40.)
36
HURRICANE
FORCES OF NATURE
Visit suggestions/questions:
Looking from above, note the shape of the hurricane table. Have you seen a symbol similar to
this on a weather map?
Spin, then stop the disk. If this were a real hurricane, where would the winds be the strongest?
Where would they be the weakest?
Sources:
“Hurricane.” Microsoft  Encarta Online Encyclopedia. Microsoft Corporation. 2002.
http://encarta.msn.com
“Hurricanes: The Eye of the Storm.” The Weather Channel. (9/25/02).
http://www.weather.com/newscenter/specialreports/hurricanes/index.html
National Weather Service Tropical Prediction Center National Hurricane Center.
http://www.nhc.noaa.gov/
Sterling, Donna R., “Science on the Web: Exploring Hurricane Data.” Science Scope. March 2002, p. 8690. (Published by the National Science Teachers’ Association. Note: an NSTA member ID is required to
read this article online.)
http://www.nsta.org/main/news/stories/science_scope.php?category_ID=87&news_story_ID=46634
The Weather Room. National Severe Storms Laboratory. http://www.nssl.noaa.gov/edu/
37
SEISMIC WAVES
FORCES OF NATURE
A computer simulation allows visitors to select a historical earthquake from a world map
and see how the resulting seismic waves traveled around and through the Earth.
Text Panel:
Hmm…
- What happens to the wavy seismogram at each station?
- Which kind of wave travels the fastest?
What’s Going On?
This program simulates the behavior of seismic waves. Some energy waves travel through the
Earth, bouncing off its solid core, while some ride along the surface. Comparing information at
different stations helps scientist locate the epicenter of the quake.
So What?
So…seismologists study earthquakes and simulate them on computer models like this. They can
learn about the composition of the hidden interior of the Earth by looking at how waves travel
through our planet.
Discover More!
- The point underground where an earthquake happens is called the focus. This is the point
where Primary and Secondary Waves are generated.
- The point directly above the focus of the quake is the epicenter, and this is where Surface
Waves are generated. Notice the surface waves travel slower than the others. Because they
last longer as they roll out from the epicenter, they cause the most damage.
The BIG Idea:
Earthquakes generate waves that move 1) deep into the Earth and 2) along its surface.
Background Information:
An earthquake is caused by a sudden movement of the Earth’s crust along a fault line.
When stress builds up in the Earth’s outer layer and push the sides of the fault together,
rocks slip. This releases energy in waves that travel through the rock to cause the
shaking that we feel during an earthquake.
Energy from an earthquake is carried by different kinds of waves. P-Waves are primary
waves that travel rapidly, compressing the earth in front of them and expanding it behind
as they pass. S-Waves are secondary waves that travel slower than P-Waves because
they move up and down or sway side-to-side. The effect of the S- and P-waves
determines the distinguishing features of an earthquake: velocity, duration, frequency and
magnitude.
Most earthquakes occur when plates grind and scrape against each other. Some parts of
the fault adapt to this movement by constant “creep” resulting in many tiny shocks and a
few moderate Earth tremors. In other areas where creep is not constant, strain can build
up for hundreds of years, producing great earthquakes when movement finally occurs.
The hypocenter is the point where the quake begins, deep in the fault. The epicenter is
the point on the surface directly above the hypocenter.
38
SEISMIC WAVES
FORCES OF NATURE
Reports to the public on the magnitude of an earthquake use the Richter scale, which is
based on readings taken from seismographs. Since this figure is based on objective data,
it may not reflect what a person feels. The Mercalli scale is based on observable damage
and effects.
Try this at School:
Epicenter Sleuths
Using a world map, the information below, and a drawing compass (or pencil on a string), locate
the epicenter of a quake, given only the distance from the epicenter at three seismograph stations
around the world.
Seismographs measure the vibrations within the Earth and can tell when the shock waves from a
quake arrive at a point, but not from where they came. By measuring the time between the
primary and secondary waves, seismologists can determine how far away a quake is. They use
this distance as a radius to draw a circle around the station on a map. Any point on this circle
could be the quake. By using information from three stations and overlapping the circles, the
epicenter can be determined as being the point at which all three circles meet.
We can now instantly share information about events around the world. You can track this
information from a newspaper, computer connection or television program and make your own
updated map of natural disasters.
Distance from Epicenter (km)
Seismic Reading:
New York City
Find and mark the 3 stations on a map.
Seattle, Washington
Draw a circle around New York City, with
with the radius being the distance from the
Rio de Janeiro, Brazil
epicenter, based on the map’s scale. If you
only had this single bit of information, where might the quake have occurred?
Draw a circle around Rio de Janeiro, Brazil, with the radius being
the distance from the epicenter. How many possibilities are there now
for the epicenter?
Draw a circle around Seattle, Washington, with the radius being the
distance from the epicenter. What is the only possibility for the quake’s
epicenter now?
(km)
3750
4250
8000
?
Note: The map (right) is not to scale and is used as an example only. An accurate map should be
used for this activity.
Visit suggestions/questions:
View the New Zealand earthquake seismic waves, then go to the Earthquake café and
experience the earthquake for yourself.
Sources
“Earthquake Hazards Program.” United States Geological Survey. http://earthquake.usgs.gov/
Glasscoe, Maggi. “Earthquakes.” The Southern California Integrated GPS Network Education Module.
Updated 8/14/98. http://scign.jpl.nasa.gov/learn/eq.htm
Pendick, Daniel. “The Restless Planet: Earthquakes.” Savage Earth. PBS Online.
http://www.thirteen.org/savageearth/earthquakes/index.html
39
TWISTER
FORCES OF NATURE
A column of mist vapor twirls into a tornado-like vortex as it moves through a four-foot
chamber. Visitors adjust the airflow to see the effects on the twister.
Text Panel:
Hmm…
- Where have you seen patterns like this?
- What happens when you block some of the air vents?
What’s Going On?
The fan creates an updraft drawing the warm mist and air in a visible funnel. In a real tornado,
a rotating column of cool air in a storm cloud merges with rising currents of warm air from the
ground, forming a vortex lifting cars, roofs, small terriers, and Kansas farm girls high into the
air.
So What?
So…small, quick storms like tornadoes are hard to predict. By studying models like this,
scientists try to learn how twisters behave and how to survive them.
Discover More!
- ‘Tornado Alley’ is an area of Texas, Nebraska, Oklahoma and Kansas where flat plains and
humid summer seasons are perfect for creating twisters.
- The smaller a storm, the harder it is to predict. Massive monsoons in India can be forecasted
with some accuracy, hurricanes with less, and tornadoes strike with little warning at all.
The BIG Idea:
Tornadoes occur when moist air is carried upward through an unstable atmosphere and
forms a vortex due to strong rotating winds.
Background Information:
A tornado is a rotating column of air that extends from a cloud (most often a
thunderstorm cloud) to the ground. Tornadoes tend to be funnel-shaped, but may
resemble a rope or may have multiple vortices. They may be filled with dust and debris,
which makes them easily visible, or may be transparent or obscured by approaching
storms.
In order for a tornado to form, there must be a great deal of moisture in the air.
Typically, a thunderstorm develops where the atmosphere is unstable; exhibiting a large
temperature variation between ground and sky. This may occur along a strong frontal
system or along a “dryline,” separating very moist warm air from hot dry air. Changing
wind direction and increasing speed accompanied by updrafts create the conditions
needed for a horizontal vortex to form low in the atmosphere. The upward-moving wind
changes the axis of the spinning air, forming a rotating vertical column that may be as
wide as six miles across. Tornadoes are often generated under these types of conditions.
A dark greenish sky, large hail, an approaching wall cloud, or a loud roar similar to that
of a freight train are all weather conditions that may indicate an approaching tornado.
40
TWISTER
FORCES OF NATURE
While tornadoes occur most frequently between 2 p.m. and 9 p.m. in April, May and
June, East of the Rocky Mountains in the United States, they may form at any time of
day, during any month of the year, almost anywhere in the world.
Tornadoes vary greatly in their severity. The wind speeds in a tornado tend to be 100
miles per hour (mph) or less but can reach more than 250 mph in some storms. While the
path of damage left behind a typical tornado is fifty yards wide and shorter than a mile
long, some paths of destruction can be as wide as one mile and as long as fifty miles.
Tornadoes may stay in contact with the ground for seconds or last for more than an hour.
Try this at School:
Tornado Alley: (Modified from “Tornado Alley: An Internet WebQuest on Tornado Formation and Safety
Factors” by Shannon Russell, a student in Geology 308: Integrated Earth Science at Texas A&M University,
Fall 2001. http://lava.tamu.edu/courses/geol308/WebQuests/TornadoWQ/TORNADO.HTM)
Introduction: Tornadoes are one of the many enigmas of nature that keep scientists on their toes.
How do they form? Why do they form in some places more than others? What makes them so
hazardous to society? How are tornadoes measured? What is the best action to take if a tornado
touches down near you? The answers are not as cut and dry as most would think. Tornadoes are
the result of converging masses of warm and cold air. With this in mind, they can form anywhere
in the world. To date, there are no sure-fire methods of predicting when and where tornadoes
form. However, there is the ability to assess conditions ripe for tornado formation. Society is in
constant threat of these deadly storms. This activity is designed to present the factors behind
tornado formation, the areas most conducive to their threat, and what action citizens can take to
protect themselves when these storms arise.
The Adventure: The National Oceanic and Atmospheric Administration (NOAA) has contracted
you to form a group of citizens who are charged with familiarizing the community with the warning
signs and hazards surrounding tornadoes.
Your task is to locate as much information as possible on
- the formation of tornadoes
- the weather patterns conducive for the formation of tornadoes
- the safety precautions your community can take to avoid devastation
- the safety guidelines to follow during the storm, and finally,
- the steps to take following the occurrence of a tornado touching down.
Your report should be presented in the format of a television news broadcast, including a special
report bulletin, weather report, and local community news. In addition to your broadcast, your
news channel will be distributing maps to the community documenting tornadoes touching down
in your community over the past thirty years. The sky's the limit! Be as creative as possible!
Each section of the news report will be assigned to groups by the instructor. Each group is
charged with reporting the most accurate and informative information as possible. Remember, the
evening news is the source of information for most citizens. Take advantage of this opportunity!
Your attempt to inform society can reap endless rewards and possibly save thousands of lives in
the future. Links provided will assist you in your task.
The Process
Groups are to be assigned by the instructor.
Make sure to read the assignment carefully.
Individual groups should work together ensuring all members maximize knowledge of their
subject material.
Individual groups should consult with one another before broadcast verifying information to be
accurate before reporting.
41
TWISTER
FORCES OF NATURE
All groups should meet before broadcast to determine a format for the evening news report.
Determine order of topics to be presented.
Groups should split responsibilities of plotting tornadoes on one chosen community map.
Roles
Special Report Team: Report the current situation of your area being under a tornado warning.
Make sure to include the differences between a tornado and warning. How do these storms form?
Make sure to include terms such as supercell and cumulonimbus clouds. Do not be overly
descriptive. It is the weather forecast group's responsibility to give details on the specific
characteristics of the formation of these storms. However, you do need to report the damage
scale and make your listeners aware of the dangers of each level of the Fujita Scale. Use
provided links to research and present accurate information. Use graphics when necessary to
provide supplements to your report.
Weather Report Team: Use the NOAA site to find information about the formation of tornadoes.
Assume your community is under a tornado warning and properly inform your citizens of the signs
to look for in the storm. Explain how this storm originated. Make sure to be as descriptive as
possible. Use as many technical terms as possible, but remember your viewers are not
meteorologists, so you will need to explain what those terms mean. Also, make sure to include
why your area is or is not more susceptible to these storms.
Local Community News: Using various search engines, find the information to provide your
community with the best safety precautions for future storms. Be sure to inform them of actions to
take now, in light of the current tornado warning. Make sure to include supplies needed, shelter
locations in your area, and any other information useful to your specific community.
Tornado Mapping: Determine whether or not your community is part of Tornado Alley. Split the
thirty-year spectrum between the 3 groups and chart your time frame on one map to be copied
and distributed to your community.
Conclusion: Hopefully, by presenting your group information, you have gained the knowledge of
how tornadoes form, how they effect your community, and above all, what you can do as a citizen
of your community to prepare and assist others in a time of need. Now take this information, and
MAKE A DIFFERENCE!
References
The Fujita Scale. http://www.tornadoproject.com/fscale/fscale.htm
National Oceanic and Atmospheric Administration. http://www.noaa.gov
Rosenberg, L. (2000) An Internet Web Quest on Chesapeake Bay Water Quality Page.
http://www.sru.edu/Depts/pcee/ProfDevInit/Resources/bayquest.htm
Visit suggestions/questions:
How does this tornado work?
What are you controlling when you press and hold the button?
How is this tornado similar / not similar to a real one?
Is air moving into or out of the holes on the side of the column? How can you tell?
Try blocking off the holes in the side of the column. What happens?
Sources:
“About Tornadoes: Frequently asked Questions.” National Oceanic & Atmospheric Administration.
Updated 2/23/01.
http://www.noaa.gov/tornadofaqs.html
42
TWISTER
FORCES OF NATURE
“Everything you want to know about tornadoes: Experts answer your tornado questions.” USA TODAY.
Updated 7/20/00. http://www.usatoday.com/weather/wtwistqa.htm#torspins
“Tornadoes.” National Oceanic & Atmospheric Administration. (8/2/02).
http://www.noaa.gov/tornadoes.html
“Tornadoes.” The Weather Channel Storm Encyclopedia.
http://www.weather.com/encyclopedia/tornado/index.html
Tornadoes…Nature’s most violent storms. A PREPAREDNESS GUIDE Including Safety Information for
Schools. U.S. DEPARTMENT OF COMMERCE. National Oceanic and Atmospheric Administration.
National Weather Service. September 1992. http://www.nssl.noaa.gov/NWSTornado/
“Vortex: Unraveling the Secrets.” NOAA Quest Series. Episode One, National Severe Storms Laboratory
and the National Oceanic and Atmospheric Administration. 1997.
http://www.nssl.noaa.gov/noaastory/book.html
“Teacher Resources.” National Severe Storms Laboratory. http://www.nssl.noaa.gov/resources/
“The Weather Room.” National Severe Storms Laboratory. http://www.nssl.noaa.gov/edu/
43
VOLCANO
FORCES OF NATURE
Visitors use pumps to add pressurized liquid and air into a transparent volcano model,
creating an eruption.
Text Panel:
Hmm…
- Can you make the volcano erupt in different ways?
- What happens to the eruption if you change the number of open vents?
What’s Going On?
A volcano, which is an opening in the Earth’s crust, can have many different types of eruptions.
In an eruption, rock and gases move from under the ground, through a vent (a weak spot), to the
Earth’s surface and into the air.
So What?
So…by studying different types of eruptions, scientists are able to better predict how and when a
volcano will erupt. This can save lives.
Discover More!
- Plinian eruptions are the most powerful type of volcanic eruption. They occur when gas
builds up under the ground over a long time. When the pressure gets high enough, the gas
explodes through one or more volcanic vents. The cloud of ash, gas and rock can shoot tens
of miles into the air at hundreds of feet per second! This was demonstrated in 1980 when
Mount St. Helens erupted in Washington state.
The BIG Idea: There are many types of volcanoes and they may produce many types of
eruptions. However, all are similar in that the pressurized material from below the
ground is conducted through a vent to a new location above the Earth’s surface.
Background Information:
There are many types of volcanoes. While these can be categorized to some extent,
volcanoes are often combinations of multiple types. Volcanic eruptions can also be
classified. Some volcanoes eject lava, while others emit gases, ash clouds or large
chunks of rock. Some volcanoes predictably exhibit one specific eruption type while
others may exhibit several types’ characteristics over the course of a single eruption.
Keeping in mind that there are many variations, types of volcanoes and eruptions are
listed below.
Types of Volcanoes
Cinder Cone / Scoria Cone
Composed of: loose grainy particles called “cinders.”
Eruption: Compressed gases eject lava into the air out of a
central vent in the bowl-shaped cone. As it moves upward,
the lava breaks into particles that cool and form cinders.
The cinders fall back around the vent to form a cone.
44
height: may be as tall as
1000 feet above base
width: may be up to one mile across
VOLCANO
FORCES OF NATURE
height: flat with the ground
Fissure Volcano
width: wide expanse
Composed of: a huge hardened
pool of lava
Eruption: a large crack opens in the Earth’s surface and considerable quantities of lava
erupt approximately 100 feet or less into the air, forming a “curtain of fire.” While in the
air, the lava remains liquid, it pools to the ground, flows slowly and solidifies. Often the
lava hardens over the fissure, leaving behind a large flat plain with no visible point of
origin. This type of eruption may also occur at the base of a volcano that contains a
central vent.
Giant Caldera
height: may be flat or miles deep
width: between one and tens of miles across
Composed of: a circular depression in the ground that may or may not be filled with lava
or volcanic ash.
Formation: Following a huge explosive eruption, enough material is displaced under the
ground that the surface layer of the Earth collapses in, forming a circular depression.
Calderas may form at the summits of other types of volcanoes, or may be volcanoes in
their own right.
height: may be several hundred feet high
Lava Dome
Composed of: layers of hardened lava. Lava domes often
width: may be hundreds of feet across
form in the craters or on the sides of other types of volcanoes.
Eruption: highly viscous lava oozes from a volcanic vent and forms a steep-sided mound
surrounding the vent. Lava pushes outward, filling the inside of the mound and breaking
through the sides. Cooling lava on the outer layers of the mound cracks off and slides
down around the edges of the mound.
Shield Volcano
height: may be tens of thousands of feet high
width: may be hundreds of miles across
Composed of: thousands of layers of hardened low-viscosity lava
Eruption: a high magma supply rate provides large quantities of low-viscosity, low-gascontent lava that spurt out of a central vent or group of vents at the summit of the volcano
or along fissures radiating from the summit. The spewing lava forms a fountain that may
reach hundreds of feet in the air. The lava then falls to the ground and flows down the
volcano, forming wide lava lakes in depressions along the volcano’s sides. The eruption
may last from a few minutes to several hours. While the lava fountain may destroy
surrounding vegetation, these types of eruptions are not particularly violent or explosive
and the lava tends to flow slowly, giving people time to evacuate if necessary. Because
these types of volcanoes tend to be commonly found in Hawaii, these eruptions are called
Hawaiian eruptions.
45
VOLCANO
FORCES OF NATURE
Stratovolcano / Composite Volcano
Composed of: layers of solid lava alternating
with layers of volcanic ash, cinders, and rock
fragments.
Eruption: very viscous magma with a
high gas content moves slowly
upward through the
volcano,
cooling and plugging its own exit
pathways to the surface. Following a long dormancy period, the pressure of pent-up
gases explodes through the blockage, sending a cloud of volcanic ash, gas, and
pyroclastic (solid volcanic material) tens of miles into the atmosphere at hundreds of feet
per second. This dense cloud, which may be sustained from hours to days, can be so
enormous that it may cause climate changes. Ash may affect areas that are hundreds of
miles downwind from the volcano.
height: may be as tall as
10,000 feet above the base
width: may be up to tens of
miles across
In addition, extremely fast-moving hot volcanic rock flows down the volcano’s sides,
triggering mudslides, and destroying everything in its path. The layers of lava, rock, ash,
and mud eventually settle down, enlarging the volcanic cone. Magma may push through
fissures in the crater or sides of the volcano, cooling and hardening to strengthen the
framework of the volcano itself. Following a large eruption of particularly viscous lava,
the whole summit of the volcano may collapse, forming a caldera.
The type of eruption described above is called a Plinian eruption. Plinians are the most
powerful and explosive of volcanic eruptions. Other types of eruptions associated with
Stratovolcanoes are Vesuvian, which result in large ash / gas plumes, and Pelean
eruptions that form avalanches of lava that may flow down the volcano at speeds up to
100 miles per hour. Pelean eruptions are often associated with the formation of lava
domes, which cap the volcano and trap gases underground until the next eruption occurs.
Other Types of Eruptions
In addition to those classifications described above, there are other types of eruptions that
may be associated with more than one type of volcano.
Hydrovolcanic Eruptions
Hydrovolcanic eruptions are associated with water. When hot magma meets water, either
on the Earth’s surface (lake or shallow sea) or within the Earth’s strata, the water flashes
to steam, rapidly expands, and explodes. The resulting steam cloud may reach several
miles in height. No new magma is erupted during this type of explosion – only steam and
rock that already exists in the volcanic conduit. Hydrovolcanic explosions are powerful
enough to fracture solidified magma, forming a very fine ash. Some eruptions may be
very brief, while others are able to sustain an eruptive plume for some time. However,
once the water supply is depleted, the eruption is over. While the rapid expansion of
steam produces a violent, explosive result, these eruptions tend to be relatively small.
They are associated with many types of volcanoes.
46
VOLCANO
FORCES OF NATURE
Strombolian Eruptions
Strombolian eruptions emit chunks of viscous magma called “blocks” or “bombs,” during
regular explosions as gas escapes while rising to the surface. Gas pressure builds up to a
high level and finally results in an explosion, fragmenting blocks of lava. These particles
travel in parabolic paths, 50 to 100 feet into the air, landing and building up around the
volcanic vent. Lava may collect on the sides of the volcano and stream down the slopes.
A small amount of ash may also be produced. Strombolian erruptions tend to be loud,
but are relatively small. While emitting impressive noises, they generally do not produce
lava flows and do not develop a sustained eruption plume. Strombolian eruptions
typically produce Cinder Cones or Stratovolcanoes.
Submarine Eruptions
Submarine eruptions occur under the ocean along mid-ocean ridge fissures. Because they
occur at great depths and water pressures, these eruptions are not necessarily noticeable at
the water’s surface. The water pressure causes the lava to roll down from the ridges in
blocks called “pillow lava.” This process may eventually form a volcanic island.
Vulcanian Eruptions
Vulcanian eruptions tend to occur after long dormancy periods. They consist of violent
and loud brief explosions that emit fragments of magma, gas, ash, cinders, and pumice.
Over the course of a few minutes to a few hours, gas and ash forms a dense cloud above
the summit, approximately 3-6 miles high. The volume of ash that is emitted is relatively
small and is usually dispersed over a wide area. The ash and pumice is blown away from
the vent and may result in small cones (less than 2000 feet high). High viscosity, highgas-content magma plugs the volcanic conduit, making it difficult for gas to escape. As
small amounts of gas build up, the high pressure eventually causes an explosive eruption.
Although lava blocks and bombs may shoot into the air during these explosions, landing
near the volcanic vent, Vulcanian eruptions are not usually associated with lava flow.
Try this at School:
Volcano!
(Source: Adapted from Weisel, Frank (Earth Science teacher, Tilden Middle School, Rockville, MD) Lesson
Plan Library, Discovery School.com. 9/2/02. http://school.discovery.com/lessonplans/programs/volcano/)
Lesson length: Two class periods
Grade level: 6-8
Objectives:
Students will understand the following:
1. Volcanic eruptions that take place near populated areas can be disastrous.
2. The level of destruction caused by a volcanic eruption depends on several factors, including
the kind of volcano eruption and the speed at which the lava or ash flows.
3. Volcanic eruptions can often be predicted.
4. Measures can be taken to help people cope with the disaster of a volcanic eruption.
Materials:
Computer with Internet access
Research materials about volcanoes
Procedure:
1. Review with your students what they have learned about volcanoes.
47
VOLCANO
FORCES OF NATURE
2. Present the following scenario to the class. The year is 2001, and a large Indonesian volcano
has erupted. It is the worst eruption in recorded history. To make matters worse, Mt. Pinatubo,
Mt. Rainier, and Mt. Vesuvius are erupting, all violently.
3. Divide the class into groups of three or four to act as teams of volcanologists assigned as aides
to the president of the United States. Each group's assignment is to give the president a report on
what can be expected to happen and what steps can be taken to help people cope with the
disaster.
4. First, have students use the Internet or other research materials to locate the volcanoes you
have mentioned and learn some background material about each one. They should answer
questions such as “What kind of volcanic eruption are we dealing with in each case?” and “How
fast is the lava or ash flowing?”
5. Instruct each group to make a logbook of its findings and recommendations. Who is in danger?
What are students' recommendations to save people and towns? How will each eruption affect
the environment? How long will the effects last?
6. Have each group present its findings to the class.
Adaptations for Older Students:
Have each student research a famous volcanic eruption in history and describe the eruption
scientifically, explaining the type of eruption and its long-term effects on the environment, as well
as its effects on human life.
Discussion Questions:
1. Volcanoes affect the Earth in many ways. Describe why 1816 was called “the year without a
summer.”
2. Discuss the importance of volcanoes to life on Earth.
3. Describe a pyroclastic flow.
4. List and describe the steps you would take to predict a volcanic eruption.
5. Describe the death of a volcano.
6. What can we expect to gain by understanding volcanic discharges?
Extensions:
Live from the Kalapana Volcano!
Have students write news accounts as if they were reporters covering the eruption in Kalapana,
Hawaii, detailing the sights and sounds of the city's destruction. Help students find references to
research the eruption. Have them prepare visuals to support their news stories and report their
stories “live” from the scene. They should include mock interviews with Kalapana citizens and
volcanologists on site. Have students lay out their articles using a computer, and display their
work around the school.
Watch Out for Vog!
Smog and its offspring, acid rain, are serious problems in some of the world's largest cities.
People create smog by burning fossil fuels. But have students ever heard of vog? Vog is like
smog that is produced by a volcano, and it is a serious problem on the Big Island of Hawaii.
During quiet eruptive phases, Kilauea generates around two thousand tons of sulfur dioxide (a
smog-causing gas) per day. Since 1986, Kilauea has been in a continuous quiet eruptive state,
with daily lava flows giving off deadly vog-causing fumes. Have students research and make lists
of the components of both smog and vog. They should compare and contrast the two lists and
describe how both smog and vog affect the quality of life. Encourage students to suggest ways to
curb both smog and vog. Have them locate Kona, Hawaii, on a map and explain why it has so
much acid rain.
48
VOLCANO
FORCES OF NATURE
Visit suggestions/questions:
How does opening one or both vents affect the
height of the eruption plume?
lava flow?
Try creating an eruption that is
primarily lava flow
primarily gaseous
How are these eruptions the same? different?
Sources:
Jansen, Jeroen, Galvin Sng, and Cameron Taggart. “Volcanoes Online.” ThinkQuest 1998 Internet
Challenge Finalist. ThinkQuest Inc. 1998. http://library thinkquest.org/17457/volcanoes/erupts.php
“Principal Types of Volcanoes.” United States Geological Survey. 2/6/97.
http://pubs.usgs.gov/gip/volc/types.html
“Surface and Interior of Earth.” Windows to the Universe. University Corporation for Atmospheric
Research (UCAR). The Regents of the University of Michigan. 2000.
http://windows.arc.nasa.gov/tour/link=/earth/Interior_Structure/overview.html
Svitil, Kathy. “Out of the Inferno: Volcanoes.” Savage Earth. PBS Online.
http://www.thirteen.org/savageearth/volcanoes/index.html
Topinka, Lyn. Volcano Types Quick Reference Guide. United States Geological Survey. Cascades Volcano
Observatory. Vancouver, WA. 7/09/01.
http://vulcan.wr.usgs.gov/Glossary/VolcanoTypes/volcano_types_quick_reference.html
“Types of Volcanic Eruptions.” United States Geological Survey. 2/5/97.
http://pubs.usgs.gov/gip /volc/eruptions.html
“Types of Volcanoes.” Wheeling Jesuit University / NASA Classroom of the Future. 2000.
http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html
Volcano World. http://www.volcanoworld.org/
Volcanoes: Can we predict volcanic eruptions? Annenberg/CPB. 2002.
http://www.learner.org/exhibits/volcanoes/entry.html
49
WHAT’S SHAKIN’?
FORCES OF NATURE
Visitors construct buildings at four shake tables, set off earthquakes, and see how the
structures hold up.
Text Panel:
Hmm…
- Which building designs stay up the longest?
- What changes can you make to your design to keep it stable longer?
What’s Going On?
Center of gravity, weight, flexibility, and wall structure all affect the stability of your design.
Because different objects vibrate more strongly at different resonances, a building’s design will
affect how it vibrates during an earthquake.
So What?
So…simulators such as these allow engineers to test and retest new theories of building designs
and see the results of different approaches.
Discover More!
- While no building will ever be totally ‘earthquake proof,’ San Francisco’s Transamerica
building (right) is a great example of an earthquake-resistant structure. The shape and
precast concrete columns at the base are designed to withstand twice the stress estimated to
be generated in a major quake.
- An average 50-story skyscraper will sway as much as 36 inches in an earthquake!
The BIG Idea:
The stability of a building during an earthquake depends on many factors.
Background Information:
The stability of a building during an earthquake depends on many factors including the
building’s mass, the location of its center of mass, its height, and the materials from
which it is constructed. All of these factors determine the building’s natural (resonant)
frequency—the frequency at which the building vibrates most easily. The greatest
damage occurs when the frequency of an earthquake is at or very close to the natural
frequency of a building.
Building characteristic
Mass
Height
Flexibility
To decrease a building’s
natural frequency,
add more mass
make the building taller
make the building more
flexible
To increase a building’s
natural frequency,
decrease its mass
make the building shorter
make the building more stiff
The frequency of an earthquake’s waves is high near the epicenter (source) and decreases
as the waves move outward. A building located near the epicenter of a quake is more
likely to be damaged if it has a high natural frequency (is low-mass, short, stiff) than if it
has a low natural frequency (is heavy, tall, flexible).
50
WHAT’S SHAKIN’?
FORCES OF NATURE
A building located at a distance from the epicenter of a quake is more likely to be
damaged if it has a low natural frequency (is heavy, tall, flexible) than if it has a high
natural frequency (is low-mass, short, stiff).
The natural frequency of a typical 2-story building may be 5.0 Hz (vibrations per second)
while that of a 30-story building may be 0.3 Hz. This means that it takes the 2-story
building 0.2 seconds to complete one full vibration while it might take 3 seconds for a 30
story building to sway back and forth.
Of course, other factors besides height affect the way that a building responds during an
earthquake, for example, the choice of construction materials. The more flexible a
material is, the more likely it is that the material will withstand a quake.
Material
Timber
Steel
Reinforced
concrete
Non-reinforced
concrete
Reinforced
Masonry
Non-reinforced
masonry
Ductility (Flexibility)
medium-high
can be bent and flexed without losing strength
high
achieved through balance of steel in tension
and concrete in compression
low
Additional Information
damps vibrations – reduces resonance
and overall building strain
similar to reinforced concrete
mortar/masonry boundaries are areas
that may fail during earthquake
easily sheared, serious hazard
very low
There are several ways that engineers attempt to quake-proof buildings. One method is
to connect the building and its foundation directly together. If the foundation of the
building moves, the rest of the building will move with it.
An alternate quake-proofing method is to create a building that moves independently of
its foundation. If an earthquake arises, the building will remain in place as the foundation
moves beneath it.
Making a building large and stiff may keep it together, assuming there are no inherent
weak spots. Designing a building so that the frame is able to move somewhat allows the
building to absorb some of the vibrations without coming apart.
Try this at School:
Demo #8: Building Resonance
(Source: Barker, Jeffrey S. (SUNY Binghamton) Demonstrations of Geophysical Principles Applicable to the
Properties and Processes of the Earth’s Interior. NE Section GSA Meeting. Binghamton, NY. March 28-30,
1994. http://www.geol.binghamton.edu/faculty/barker/demos/demo8.html)
Purpose:
Demonstrates how buildings respond to seismic shaking
Supplies:
Cardboard, stiff paper (such as postcards or computer cards)
Background and Demonstration:
51
WHAT’S SHAKIN’?
FORCES OF NATURE
Earthquakes generate seismic waves with a broad spectrum; that is, the waves can shake over a
fairly broad range of frequencies. As these waves propagate away from the earthquake source,
however, anelastic behavior of the rocks of the crust and uppermost mantle, cause the higher
frequency components to be damped out. Thus, the farther a seismic wave propagates, the less
high-frequency energy it will contain (this is called anelastic attenuation). The response of a
building to shaking at its base due to seismic waves depends on a number of factors related to its
design and construction. However, one of the most important factors is simply the height of the
building, because this determines the frequency of resonance of the building. Short buildings
have a high resonant frequency (short wavelength), while tall buildings have a low resonant
frequency (long wavelength). In terms of seismic hazard, therefore, short buildings are
susceptible to damage from high-frequency seismic waves from relatively near earthquakes. On
the other hand, tall buildings are at risk due to low-frequency seismic waves, which may have
originated at much greater distance.
A simple model to demonstrate of the effects of building resonance may
be constructed using cardboard and stiff paper (we use postcards and old
computer cards). Make two parallel folds in the paper so that you have an
inverted "U" shape, then fold out the ends so that they may be attached
(by tape or staples) to the cardboard base (a box in our case). Now
attach more inverted "U"-shaped papers on top of the first to build up a
tower. These should all be attached on the same sides so that the tower
can oscillate in one direction (you should be able to see through it one way).
Build two towers of different heights attached to the same base and oriented
in the same direction. Now, if you shake the base slowly (low frequency),
the taller building will sway back and forth, but the shorter building will remain
upright and simply move along with the base. On the other hand, if you shake the base quickly
(high frequency), the shorter building oscillates, and while the taller building may deform with a
variety of S-shapes, it will not sway back and forth as a unit.
Appropriate modifications may be made for science fairs or more permanent exhibits. The
buildings may be constructed out of sheet metal or any other flexible material, as long as it is free
to move in one direction. A source of shaking may be constructed with a toy motor powered by a
variable transformer, using an off-center arm-and-wheel arrangement to shake the base back and
forth.
Visit suggestions/questions:
Quake Challenge!
Before your visit, using equal numbers of cocktail straws and balls of clay, have your students
compete to make the tallest, strongest structure to withstand an earthquake. Bring the buildings
to the SciQuest gallery and place them, one at a time, on the What’s Shakin’? tables. Have the
students determine which design stays up the longest.
While the flimsiest structures will collapse first, those built too rigidly
will also suffer damage. Structures designed to ‘give’ a little during
the quake will hold up the best.
Did your students discover pyramids or domes?
Variations:
Devise a scoring system that rewards consideration of conservation of materials, elegance, or
creativity of design.
Instead of giving students equal amounts of material, use play money and have students ‘pay’ for
materials of differing quality and price. Is the most expensive structure the sturdiest? How does
economics affect building design?
Have students write architect specifications for building in earthquake-prone areas.
52
WHAT’S SHAKIN’?
FORCES OF NATURE
Other things to try:
Using the building materials found at the exhibit, build a structure that:
has a fixed foundation
has no foundation
stands up when you place it one way on the table, but falls over when you place it on another
way
is as tall as possible
is a pyramid
Which one of your building designs best holds up to a quake?
Try testing the effect of changing the position of a building’s center of mass.
Using the three resonance rods (on the What’s Shakin’? table containing
Legos), move the triangles up and down the rods in order to change the rods’ center of mass
positions. Press the “on” button and see what happens.
Note: with respect to the table containing Lincoln Logs:
John Lloyd Wright, son of Frank Lloyd Wright designed and developed Lincoln Logs in 1916.
John was inspired by the construction techniques his father used when creating the foundation of
the Imperial Hotel, an earthquake-proof building in Tokyo. (Source: http://www.historychannel.com)
Sources:
“Earthquake Hazards Program.” United States Geological Survey. http://earthquake.usgs.gov/
“How Do Earthquakes Affect Buildings?” FAQs: Earthquakes and Earthquake Engineering.
Multidisciplinary Center for Earthquake Engineering Research. Research Foundation of the State
University of New York. 2002. http://mceer.buffalo.edu/infoService/faqs/eqaffect.asp
Kiger, Patrick J. et.al. Great Quakes. The Learning Channel. Discovery Communications Inc. 1999.
http://tlc.discovery.com/tlcpages/greatquakes/greatquakes.html
(includes an interactive on-line make-a-quake simulator)
Pendick, Daniel. “The Restless Planet: Earthquakes.” Savage Earth. PBS Online.
http://www.thirteen.org/savageearth/earthquakes/index.html
“Resonant Rings.” Exploratorium Snacks. The Exploratorium. CA. 2002.
http://www.exploratorium.edu/snacks/resonant_rings.html)
Scott, Dr. Alan. “Effects of Earthquake Ground-Shaking on Structures.” Geology and Soil Mechanics.
UW-Stout. Updated April 5, 2000. http://physics.uwstout.edu/geo/quake_resp.htm
“Seismic Sleuths.” Earthquakes: A Teachers Package for Grades 7-12. The American Geophysical Union
Washington, DC. http://www.fema.gov/pdf/library/seismic.pdf
VanCleave, Janice. “Earthquakes and Resonance: Science for Fun – Surprising Science Facts.” Science
Fair Central. (10/17/02).
http://school.discovery.com/sciencefaircentral/jvc/surpscifacts/equakes_resonance_shaker.html
53
WHEEL OF DISASTER
FORCES OF NATURE
Visitors spin two wheels, representing their percent chances of 1) dying in a natural
disaster 2) dying in a specific type of natural disaster.
Text Panel (Wheel 1):
Hmm…
- Spin the top wheel!
- What are your chances of dying in a natural disaster?
What’s Going On?
If you live in the United States, your chances of dying in a natural disaster are very, very slim.
On average, only 400 people die each year from natural disasters in the U.S.
So What?
So…while it’s very rare for someone in the U.S. to die from a natural disaster (your chances are
1 in 703,555), it’s still more likely than your chances of winning a lottery (1 in 80,000,000) or a
typical product give-away contest (1 in 5,000,000).
Text Panel (Wheel 2):
Hmm…
- But, if you were to die in a natural disaster in the United States, what are you most likely to
die from?
- Spin the bottom wheel!
What’s Going On?
While disasters like earthquakes and hurricanes may get a lot of media coverage, more
Americans die in floods every year. Tornadoes, winter storms and lightning also kill hundreds of
people every year.
So What?
So…it’s important to know what types of natural disaster may occur where you live. Be prepared
and take disaster warnings seriously.
Wheel 2:
Dust Storm Earthquake
Thunder Storm
Lightning
Avalanche
Mud Slide
Winter Storm
Tornado
Hurricane
Coastal Storm
Hail
Water Spout
Flood
54
WHEEL OF DISASTER
FORCES OF NATURE
The BIG Idea: Dying as the result of a U.S. natural disaster is less likely than one might
think.
Background Information:
Around the world, natural forces disrupt the lives of millions of people each year. These
events receive a great deal of press coverage, leading to the public perception that deadly
natural disasters occur quite frequently.
In truth, the chances of a person in the United States dying in a natural disaster are quite
small.
The total U.S. population is approximately 281,422,000 people*.
The average annual number of deaths in the U.S. is 2,404,600 people.
The average annual number of deaths in the U.S. that are attributed to natural disasters is
400 people.
This means that in the U.S.
(2,404,600 / 281,422,000) x 100% = .85% of the population will die in any given year.
The annual death rate attributed to natural disasters for the U.S. population is
(400 / 281,422,000) x 100% = .000142% or approximately 1 in 703,555.
*Notes:
•
Wheel 2 does not include all types of U.S. natural disasters. Due to the difficulty of
obtaining consistent statistics, the following disasters have been omitted: drought,
forest fires, heat waves, and volcanic eruptions.
•
Information gathered from statistics from the National Weather Service 1995-2000
and the 2000 United States Census.
Try this at School:
How Often Will Severe Weather Occur Near Me?
(Source: D.S.Z. Updated March 25, 2002. http://www.nssl.noaa.gov/ideas/simplemath.html)
Introduction
Do you know what your risk from severe weather really is? On one hand, you may recall severe
weather warnings for your area a few times a year, but on the other hand, you may not have seen
any severe weather at your home in a long time, if ever. Tornado alley has started to gain a
reputation as being a place where tornadoes skip across the plains often. It's easy to gain that
impression from watching science shows on TV, but it probably isn't very accurate. Your own risk,
wherever you are, may be higher - or lower - than you think.
Tornadoes and other kinds of severe weather are rare events, making reliable statistics difficult
(we'll talk more about that in another, higher-level section). If you take severe weather reports too
literally you could easily draw a bad conclusion. So one of the scientists at the NOAA National
Severe Storms Lab used very conservative methods to calculate the risk for thunderstorm winds,
hail, and tornadoes nationwide. He knew which years of data were most reliable for different
kinds of weather reports and you may notice that in the maps we look at.
55
WHEEL OF DISASTER
FORCES OF NATURE
One problem with severe weather reports is that severe weather is generally only reported where
people are there to see it. Not surprising, but that means no one really knows how often severe
weather occurs where population density is low. Severe weather is often very localized. In fact,
the average tornado lasts only 7 minutes. Many are shorter-lived and may occur over open land,
never hitting a man-made structure.
(By the way, if you are not familiar with the Fujita scale, take minute to learn about it before going on. My
favorite site for learning about the Fujita Scale is the Tornado Project, a site created by a former teacher and
one of NSTA's SciLinks. http://www.tornadoproject.com/ Click on "The Fujita Scale.")
Maps and Risk
Dr. Brooks' work resulted in a series of maps and graphs that are on NSSL's web site under
Severe Thunderstorm Climatology (http://www.nssl.noaa.gov/hazard/). One section of the site has
maps of the total threat for the year from various kinds of severe weather.
The map shows the
number of tornado days
within 25 miles of a point.
A tornado day is a day
upon which at least one
tornado occurs. This map
is easy to read because
it's in tornado days per year.
For example, people in
central Oklahoma can
expect to have a tornado
within 25 miles of them
on 1.2 to 1.4 days / year.
We can still make some
math out of this, though.
How many years would it
take to get an even number
of tornado days? Depending on what you teach, you might start by converting 1.2 days/year to a
fraction. No matter how you calculate it, you should find that central Oklahoma can expect 6
tornado days each five years.
What is the risk where you are? If you are in an area of black, use another area in the colored
contours. This map includes all tornadoes, even the really weak ones. Let's see how often F2
and greater tornadoes might occur.
This map shows how often
you would expect an F2 or
greater tornado within 25 miles
of you. Notice, though, that it is
in days per century.
So, how many?
Central Oklahoma is colored
orange, meaning
35-40 days / century. What does
that mean? Let's divide 35 into
100. Looks like 2.86 years / F2
tornado. Forty into 100 is 2.5. So
central Oklahoma can expect an
F2 or greater within 25 miles
about once every 2.5 to 3 years.
What about the really bad tornadoes - the F4s and F5s?
56
WHEEL OF DISASTER
FORCES OF NATURE
Now we're up to the really bad stuff - F4 and stronger tornadoes.
These are also very rare, as you
may have seen on the Tornado
Project web site. And notice
now the map is in
days per millenium. The peak is
50-55 days / millenium in south
central Oklahoma. Divide
1000 by 50 (or 55) to see
that folks in south central
Oklahoma can expect an F4 or
stronger tornado within 25 miles
of them about once every 20
years.
Extending this exercise
This exercise can be extended
to include other graphics from
the Total Threat section of the Severe Thunderstorm Climatology web site for F4 and greater,
winds 50 kts or more, hail at least 3/4" diameter. (http://www.nssl.noaa.gov/hazard/totalthreat.html)
Visit suggestions/questions:
Have each student spin Wheel 1 and then Wheel 2 and record his / her results for each.
Create a class chart or graph showing the number of students that landed on each type of
disaster.
Flo
od
Ha
il
To
rna
do
M
ud
Sli
de
Lig
htn
ing
10
9
8
7
6
5
4
3
2
1
0
Ea
rth
qu
ak
e
# of students
Example:
(Wheel 2)
Sources:
“Disasters: A deadly and costly toll around the world.” United Nation’s International Decade for Natural
Disaster Reduction: World Disaster Reduction Day. October 8, 1997.
http://www.fema.gov/pdf/library/stats.pdf
Natural Hazards Center at the University of Colorado, Boulder. http://www.colorado.edu/hazards/
“Natural Hazards Data.” National Geophysical Data Center.
http://www.ngdc.noaa.gov/seg/hazard/hazards.shtml
“Teacher Resources.” National Severe Storms Laboratory. http://www.nssl.noaa.gov/resources/
57
WILD WINDS
FORCES OF NATURE
Visitors manipulate conditions on a computer weather map, then see how the pressure
systems and winds across the continent react.
Text Panel:
Hmm…
- What happens as you move the high and low pressure areas?
- Can you make a hurricane-like spiral?
What’s Going On?
This program simulates the behavior of air around low and high pressure systems. As you move
the pressure areas, the pattern of winds across the country change. In real life, these systems are
responsible for our weather.
So What?
So…meteorologists use their knowledge of how these pressure systems interact to predict our
weather. This computer system is a simple version of the complex ones they use.
Discover More!
- Click on the button to change hemispheres. Notice the direction of the winds reverse. This is
the Coriolis effect, and is due to the rotation of the Earth.
- Wind and weather across the surface of our planet are affected by a variety of surfaces –
smooth waters, rough mountains or large cities. One of the reasons hurricanes slow down is
the greater friction between air and ground when they hit land.
The Big Idea: Weather patterns are influenced by differences in air pressure across large
areas, and by the effects of the Earth’s rotation.
Background Information:
Air masses tend to move from areas of high pressure (H) where there are a
large number of air molecules per unit volume, to areas of low pressure (L)
where there are fewer air molecules per unit volume. If the Earth did not
rotate, the movement of air would be directed in straight lines from high
pressure to low pressure, as shown. >
direction of air
movement indicated by
arrows
H
H
L
H
H
Because the Earth rotates on its axis, the movement of air masses becomes a bit more
complicated.
N
As viewed from above the North Pole, the Earth
rotates counterclockwise on its axis. Since every
point on Earth rotates about Earth’s axis one time
per day, everything in contact with the ground
moves in the same direction and with the same
rotational velocity. For this to happen, points at
different latitudes on the Earth must move at
different linear (Eastward) speeds. A point at the
Equator must move more quickly toward the East
than a point near a pole.
slower Eastward
linear speed
Equator
faster Eastward
linear speed
slower Eastward
linear speed
S
58
direction of
Earth’s rotation
WILD WINDS
FORCES OF NATURE
An air mass that leaves the ground and moves toward the North or South is actually
moving in several directions at the same time.
According to Newton’s First Law, an object in motion will continue in motion with a
constant speed, in a
straight line, until an
North Pole
external force is applied
direction of
to the object.
Earth rotation
Once an air mass is
above the Earth’s
surface, it will continue
to move at its initial
linear speed to the East
(a result of the Earth’s
rotation) and will also
move in its Northward
or Southward direction.
As the air mass moves
more North or more
South from the Equator,
its Eastward linear speed
will eventually be
greater than that of the
ground. To someone
moving along with the
Earth, the path of the air
mass will appear to bend
toward the East.
Northern
Hemisphere
H
H
L
H
direction
of
hurricane
airflow
H
Equator
H
H
L
H
H
Southern
Hemisphere
direction
of
hurricane
airflow
If the air mass is moving
away from either pole
South Pole
towards the Equator, its
Eastward linear speed
will eventually be less than that of the ground and to someone moving along with the
Earth, its path will appear to bend toward the West.
If the air mass moves in an East-West direction, its path will also seem to deviate from a
straight line because the definition of East or West at a given point on the Earth will
change over time as the Earth rotates.
The apparent bending of a “straight” trajectory in a rotating system is called the Coriolis
Effect and is named after Gustave-Gaspard Coriolis (1792-1843), a French engineer and
59
WILD WINDS
FORCES OF NATURE
mathematician, who first explained how the Laws of Motion could be used in a rotating
frame of reference.
The Coriolis Effect is responsible for the formation of weather patterns such as
hurricanes. Once air begins moving from high-pressure areas to low-pressure areas, it
will begin to deviate from its straight-line path in accordance with the Coriolis Effect.
The air will continue to move toward the center of the low pressure area, but will be
deflected to one side or the other, depending on whether the system is in the Northern or
Southern Hemisphere.
For example, in the Northern Hemisphere, high-pressure air would move
toward the center of a low-pressure area but would deflect to the right of
the low-pressure center. The high-pressure air would continue to
move toward the low-pressure center, and would continue to be
H
deflected to the right. A circular wind pattern would develop,
with the wind moving in a counter-clockwise direction. This is why
hurricanes in the Northern Hemisphere always turn in a counter-clockwise
direction. Similarly, hurricanes in the Southern Hemisphere always turn
in a clockwise direction.
Northern
H Hemisphere
L
H
H
NOTE: CONTRARY TO POPULAR SCIENCE MYTHOLOGY, THE CORIOLIS
EFFECT HAS NOTHING TO DO WITH THE DIRECTION THAT THE WATER IN A
SINK, TOILET, OR BATHTUB ROTATES AS IT GOES DOWN THE DRAIN. While
the Coriolis Effect does influence the paths of large fast-moving objects that span many
latitudes, such as hurricanes or airplanes, it is much too small an effect to overcome the
other forces moving water down a drain. The direction from which water enters a sink
(or a flushing toilet), irregularities in the shape of the basin, convection currents moving
through the water, and the shape of the drain, have much more to do with the exiting
water’s rotation than the Coriolis Effect will ever have.
Try this at School:
The Coriolis Effect
(source: “Atmosphere Activities Information-Rich Problem Solving Activities Using Integrated Technology:
The Coriolis Effect.” Department of Mathematical Sciences: Mathematics, Math Education, Statistics.
(7/31/02) http://www.math.montana.edu/~nmp/materials/ess/atmosphere/expert/activities/coriolis/index.html)
Learner Objectives
By completing this lesson, the learner will:
- compare weather systems in the northern and southern hemisphere.
- make drawings to justify generalizations.
- use simple apparatus to demonstrate the Coriolis Effect.
- follow the mathematical development of the Coriolis Effect.
Exploration
Consider current weather systems found worldwide. Describe any rotating patterns you see; are
there any noticeable differences between the northern and southern hemispheres? Follow other
map links found at The Weather Channel Web Site to verify your generalizations. Make quick
sketches to justify your position.
Demonstration
60
WILD WINDS
FORCES OF NATURE
Part I: The Coriolis Effect can be easily and cheaply demonstrated with a circular piece of
cardboard like that which comes with pizza. Pin or nail the cardboard so that it is allowed to rotate
freely. Rotate it smoothly with one hand, and with the other hand draw a straight line from the
center towards a particular fixed direction. You should notice a definite spiral to the line, despite
the fact that the hand movement was linear. Repeat the demonstration by rotating the cardboard
in the opposite direction; you should be able to draw some conclusions about the direction of
apparent deflection in the Northern Hemisphere versus the Southern Hemisphere.
Teacher Directed Questions:
What happened to the line as you rotated the cardboard?
What happens to the line as you get further toward the edge?
Use mathematics to describe what happened to the curve. (use trigonometry)
What happens if you spin it fast or slow?
Look at a satellite image, observe the pattern of air masses, and how does this explain the motion
of the air masses?
You can do the same demonstration as above with a chalkable globe. This is more expensive,
but very realistic and an excellent way to firmly fix the concept of the Coriolis Effect in your mind.
Teacher Directed Questions:
Is there any other way you can demonstrate the Coriolis Effect?
Essay Question-- Demonstrate that the Coriolis Effect in the southern hemisphere is a mirror
image of that in the north, that is, air masses curve to the left no matter which direction they
move, including East-West.
Visit suggestions/questions:
At the computer kiosk:
View the demonstration / instructions.
Add high and / or low-pressure areas to the map.
Drop weather balloons on the map and see how the air currents make them move.
Use the weathervane icon to track the speed of the wind.
Stop the rotation of the Earth and see what happens.
Sources:
“Coriolis Force, an Artifact of the Earth’s Rotation.” University of Illinois Online Guide to Meteorology:
Forces, Winds. http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/crls.rxml Includes a QuickTime video.
Fraser, Alistair B. “Bad Coriolis .” Penn State University, Department of Meteorology. College of Earth
and Mineral Sciences. (7/31/02). http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html
Van Domelen, David J. “Getting Around the Coriolis Force.” The Ohio State University Department of
Physics, Physics Education Research Group. Updated November 15, 2000.
http://www.physics.ohio-state.edu/~dvandom/Edu/newcor.html
“Gaspard Gustave de Coriolis” The MacTutor History of Mathematics Archive. School of Mathematics and
Statistics. University of St. Andrews, Scotland. July 2000.
http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Coriolis.html
Audio Visible and Visible Vibes are two distinct activities that are connected together. In
both cases, visitors manipulate sound waves that are emitted from speakers and watch the
effects on small pellet-like materials.
61
AUDIO VISIBLE / VISIBLE VIBES
Audio Visible: Visitors change the frequency
and amplitude of sounds emitted by two
speakers. The sound waves from the speakers
travel towards each other through the air inside
speaker
a clear tube. The sound energy is transferred to
Styrofoam pellets sealed in the tube, producing visible
waves. Changing the frequency of the sound changes the
wave in the pellets.
WAVES
speaker
beads
drumhead
Visible Vibes: Visitors vary the frequency of a sound produced by a
speaker. Sound waves emitted from the speaker travel
several inches through the air to a drumhead. The energy in the
sound waves causes the drumhead to vibrate. This energy is then
transferred to small plastic beads sitting on the drumhead. The moving
beads’ patterns change as the frequency of the sound is varied.
sound
waves
speaker
Audio Visible Text Panel:
Hmm…
- How does changing the sound volume affect the waves?
- How does changing the frequency affect the waves?
What’s Going On?
The speaker is sending out sound waves – physical movement of the air. As these pulses go out
and echo back, they move the light Styrofoam pellets, creating visible sound waves. Greater
energy from louder sounds makes bigger waves.
So What?
So…there are many events or objects that are “invisible” to us. By using devices like these to see
and understand the unseen, we learn more about our world.
Discover More!
- Frequency is the number of times an object vibrates in one second. Clamp a plastic ruler
over the edge of a table and snap it. The number of times it vibrates per second is its
frequency.
- At certain frequencies, the outgoing and returning waves reinforce each other, creating a
non-moving, “standing” wave.
Visible Vibes Text Panel:
Hmm…
- How does the pitch (highness / lowness) of the sound affect the way the beads move?
- Can you make all of the beads move at the same time?
What’s Going On?
The sound waves from the speaker vibrate the air, carrying energy to the drumhead. The
drumhead vibrates, passing the energy to the beads, causing them to bounce. The amount of
energy carried by the waves is related to the sound’s pitch (highness / lowness).
So What?
62
AUDIO VISIBLE / VISIBLE VIBES
WAVES
So…sound carries energy that can make things (like your inner ear parts) move. If you crank up
the volume, this energy can be great enough to damage your ears.
Discover More!
- Sound needs a medium (like air, water, or wood) to travel through. In the vacuum of space
where there is no medium, there is no sound.
- Animals can hear some sounds that we cannot. Dogs can hear ultrasound (very high
pitches), while elephants and whales can hear infrasound (very low pitches).
What to do:
Put your hand - palm up - over the orange hand. Slowly raise or lower your hand to control the
frequency (pitch) of the sound. What happens?
How does this sensor work?
This sensor sends out an ultrasonic wave. When the wave hits your hand, the wave is reflected
back to the sensor. The sensor times how long it takes the wave to return. Based on this time, the
sensor sends signals to the speaker to adjust the pitch of the sound.
The Big Idea:
Sound carries energy through a medium in the form of
pressure waves.
Background Information:
Sound is generated by vibrating objects. The vibrations
produce waves that have areas of high and low pressure.
The low-pressure areas are called rarefactions, while highpressure areas are called condensations. Each
condensation and rarefaction make up a sound wave.
One
wavelength
Condensations
(pulses of higher
air pressure)
speaker
Rarefactions (pulses of
When a speaker emits sound, the cone’s vibrations transfer
lower air pressure)
energy to the air molecules located next to the speaker.
Pulses of varying air pressure travel outward from the cone through the air. Note that the
pulse travels through the air, not the air molecules themselves.
When the sound wave reaches an object (e.g. a drumhead, small pellets) the energy is
transferred from the air molecules that are next to the object’s surface to the molecules
making up the object itself. This causes the object to vibrate. The amount of motion that
is observable depends on the characteristics of the object itself.
Try this at School:
Seeing Sound
(source: Teacher’s Pre- and Post-visit Activities. Ann Arbor Hands-On Museum.
http://www.aahom.org/pathways/Sound/4_PW_SD_ACT_SS.html)
Materials (Per pair of students):
- Empty cardboard oatmeal container
or medium-sized aluminum can
- Duct or electrical tape (to cover sharp
edges if using aluminum can)
- Large balloon or latex glove
- Rubber band
- Puffed wheat or rice cereal
- Stereo
63
AUDIO VISIBLE / VISIBLE VIBES
WAVES
Procedure:
1. Remove both ends of the can or cardboard container.
2. From the balloon or glove, cut a sheet of rubber large enough to stretch across one opening of
the can or container.
3. Secure the rubber to the container with the rubber band to create a simple drum.
4. Sprinkle some puffed cereal on the rubber surface of the drum.
5. Gently tap the drum. What kind of sound do you hear? What happens to the cereal?
6. Hold the drum above your mouth, keeping the drumhead level so the cereal doesn’t fall off.
Speak loudly into the opening on the bottom.
7. Have your partner watch the cereal carefully and describe what happens.
8. Switch places and let your partner speak into the drum bottom while you watch the cereal.
What happens to the cereal as you speak into the drum? Why do you think it happens?
9. Take turns holding the open end of the drum over a speaker playing loud music.
Describe what happens to the cereal sitting on the drum’s surface.
10. Adjust the volume on the stereo. What happens to the cereal?
Discussion:
When you speak, vibrations of air travel in sound waves from your lungs, vocal cords, and mouth.
When these vibrations of air hit the underside of the drum, they transfer their energy from the air
molecules to the drum surface to the cereal sitting on the drum surface. The cereal starts to move
and shake, or vibrate. You can see the sound you made as it bumps into the cereal. The same
thing happens as the sound waves from the stereo hit the drum surface.
Visit suggestions/questions:
Audio Visible:
What happens to the balls when you increase the frequency?
What happens to the balls when you increase the amplitude (volume)?
Can you create standing waves (waves that don’t travel horizontally)?
Visible Vibes:
What happens to the beads as you move your hand under the sensor?
Do you notice any correlation between the height of your hand over the tabletop?
Do you notice any correlation between the sound that is generated, and the particular beads that
move?
Can you find a frequency at which the beads form an obvious pattern?
Sources:
Churchill, E. Richard. Amazing Science Experiments with Everyday Materials. Sterling, 1991.
Hartshorn, Robert L., et al. “Magnetism.” Physical Science Activities Manual. Center of Excellence for
Science and Mathematics Education at The University of Tennessee at Martin. Martin, TN. 1994.
http://cesme.utm.edu/resources/Science/PSAM.html
Hewitt, Paul G. Conceptual Physics, A High School Physics Program. Menlo Park, CA: Addison Wesley,
1987.
64
ECHO TUBE TUBE TUBE
WAVES
Visitors make sounds that create echoes while leaning inside a 60-foot-long tube.
Note: Toy fruit bats hang from the ceiling above the exhibit in order to represent those
animals that navigate with sonar. Fruit bats, however, DO NOT use ultrasound to
navigate.
Text Panel:
Hmm…
- Lean down to listen in the tube, then make a sharp clap with your hands.
- Try making different sounds!
What’s Going On?
When you clap, the sound travels in all directions. Some sound waves travel straight down the
tube while others bounce along the inside walls. The waves that bounce take longer to echo back
than the straight ones, so the echo you hear is distorted.
So What?
So…echoes can be used to judge distances from an object. Bats can determine their location by
sorting out echoes that return from sounds they make.
Discover More!
- Some cameras use sound waves to help them focus. They send out a sound, then measure the
time it takes for that sound to bounce back from the object they are pointing at. Using the
known speed of sound, the camera calculates the distance.
- Your first baby picture might have been taken with sound waves. Sonograms are now a
common way to ‘see’ inside the human body to take pictures of a developing baby.
The BIG Idea: The time it takes for a sound wave to echo off an object depends on the
distance that the sound wave travels.
Background Information:
Sound waves have different frequencies (pitches) and amplitudes (volumes). While the
speed of all of the sound waves traveling through a given medium is always the same, the
speed of sound does vary with the medium through which the waves are traveling.
In the air, the speed of sound varies with temperature and humidity. However, these
variations are fairly slight. In general, the speed of sound is approximately .21 miles /
second, which means that it takes approximately 5 seconds for sound to travel 1 mile.
An echo is a sound produced by sound waves that have bounced off of a surface.
The Echo Tube Tube Tube is 60 feet long. When a person
claps at the open end of the tube, some of the generated sound
waves travel straight to the closed end of the tube, reflect off,
and travel straight back to the person. These waves travel a total distance of 120 feet.
This means that it should take:
65
ECHO TUBE TUBE TUBE
WAVES
1 mile
5 seconds
x
= .114 seconds
5280 feet
1 mile
for these waves to travel to the end of the tube and back.
120 feet x
The sound of a clap travels out in all directions, away from the hands
that produce it. Many of the sound waves move outward at an angle and bounce off the
inside of the tube. These waves reflect back and forth along the tube and take much
longer to return than those that reflect directly off of the closed
end. The amount of time that it takes for these waves to return
depends on the number of reflections inside the tube.
The Echo Tube is sufficiently long that the differences in return
time are noticeable to the listener.
The first waves to return are those that bounce directly off of the end of the closed tube.
These are closely followed by the waves that have the fewest number of reflections inside
the tube. The last waves to return are those that are reflected the most often off of the
Echo Tube’s walls.
More waves will bounce off of the tube’s end relatively
quickly than will reflect a large number of times. Initially,
the listener will be bombarded by returning sound waves.
This means that the sound pulses return at a high frequency
(a large number return per fraction of a second). Because
high frequency is correlated with high pitch, the initial pitch of the echo is high.
As the frequency of returning sound pulses decreases (a smaller number return per
fraction of a second), the pitch decreases, so the pitch of the returning echo becomes
lower over time. This is the reason why the listener hears the pitch of the returning echo
change from high to low.
Try this at School:
Echo distance
(Source: The Discovery Museum. Eureka, CA. http://www.northcoast.com/~discover/kids_invent_ex4.html )
Materials:
- two wood blocks
- large solid wall
- measuring tape
Clap two wood blocks together near a solid wall and walk away from the wall while continuing
clapping. When you are about 40 or 50 feet away you will hear an echo.
Sound travels away from the blocks in all directions. The sound that hits the wall bounces off to
travel in a new direction. You hear the sound as it goes out away from the blocks. You hear the
sound again when the reflected sound reaches you. When you are close to the wall the two
sounds are so close together that they seem to be a single noise. You only hear the echo when
the two sounds are separated by at least about 1/10 of a second. Since sound travels at about
1120 feet per second, in 1/10 of a second it will go 112 feet. If you are 56 feet away from the wall
the sound will travel 56 feet to the wall and 56 feet more back to you for a total of 112 feet.
66
ECHO TUBE TUBE TUBE
WAVES
Visit suggestions/questions:
Lean in and clap your hands inside the tube. What do you hear?
How is the sound different than when you clap your hands outside the tube?
Sources:
Eby, Denise and Robert B. Horton. Physical Science. NY: Macmillan, 1986.
“Echo Tube Exhibit Graphics” The Exploratorium. CA.
http://heis enberg.exploratorium.edu/eguide/720/echotube/english_text.html
67
EDISON PHONOGRAPH
WAVES
Visitors view a reproduction of an Edison Phonograph. As staffing allows, exhibit floor
presenters open the case, and demonstrate how the phonograph works, recording a voice
on foil and playing back the recording.
Note: if you wish to have the Edison Phonograph demonstrated during your visit, please notify the registrar
when you make your group reservation.
Text Panel:
Hmm…
- What do the aluminum foil, the wax cylinder, the vinyl record and the CD have in common?
- How are they different?
What’s Going On?
When you speak into the horn, vibrations from your voice vibrate the needle. This makes bumps
on the foil. To hear the sound, the process is reversed. The bumps on the foil vibrate the needle
that vibrates the horn that vibrates the air and you hear what was recorded.
So What?
So…while the technology has changed, the basic goal - to be able to capture, record, and then
play back sound waves - remains the same from an Edison Phonograph to your CDs.
Discover More
- A flat vinyl record contains one long pitted groove that spirals inward from the outer edge of
the record. A needle runs along the V-shaped groove, vibrating as it bounces off of pits cut
into both sides of the V.
- On a CD, sound is imprinted as ridges. The ridges represent numbers. A CD player’s laser
and sensor detect the ridges. A computer uses this information to determine the encoded
numbers, which are converted into electrical signals and used to reproduce the sound.
The BIG Idea:
For more than 100 years, various technological devices
have allowed us to record and save sound waves for
future playback.
Background Information:
Thomas Edison patented the first phonograph in 1878.
Recording and playing back sound using an Edison
phonograph was a multistep process. A cylinder was
Photo courtesy of the U.S. Department of
covered with tin foil. A crank was turned at one end of
the Interior, National Park Service,
the phonograph, simultaneously turning the cylinder and
Edison National Historic Site
moving it along on a shaft. In order to record sound
waves
(for example, a person singing), the person would sing into a funnel-shaped “horn.” The
sound waves would reach the bottom of the horn, causing a stylus assembly to vibrate.
The stylus needle, placed in direct contact with the cylinder, left a groove of varying
depth imprinted in the foil.
68
GEORG’S WAVE
WAVES
To play back the recorded sound, the stylus was lifted and the cylinder
was rewound to its initial starting point. The stylus was replaced
and as the crank turned the cylinder, the needle bounced up and
horn
down along the imprinted foil. The stylus’ vibrations were
amplified by the horn, producing sound waves loud enough for
someone standing near the phonograph to hear.
stylus
cylinder
foil
Try this at School:
Phonograph Needles
(Source: Eby, Denise and Robert B. Horton. Physical Science. NY: Macmillan, 1986.)
Investigate how a record reproduces sound by doing the following. Roll a piece of notebook
paper into a cone. Make the narrow end as pointed as possible. Stick a straight pin firmly
through the pointed end of the paper cone at a 90° angle. Put an old record (one you do not
need any more) on a turntable. Turn on the record player, leaving the needle up. Touch the
straight pin in the paper cone lightly to the surface of the spinning record and listen.
Visit suggestions/questions:
Phonograph Modifications
While the Edison Phonograph in the SciQuest gallery is a replica of the original, one major
modification has been made in terms of its operation. In Edison’s times, when a recording was
played back, the listener needed to stand near the horn in order to hear the sound, particularly if
there was background noise in the room.
During the day, as staffing and scheduling allows, Exhibit Floor Presenters may open the case
and demonstrate how the Phonograph operates for visitors. In order to do this in the SciQuest
gallery, which is unlikely to be quiet at any given time, an amplifier has been installed for use
during playback. This enables visitors to hear the recorded sound’s quality.
Sources:
Bloomfield, Louis A. “Phonograph.” How Things Work. 2002. howthingswork.virginia.edu
“Edison, Thomas Alva.” Microsoft  Encarta Online Encyclopedia. Microsoft Corporation. 2002.
http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761563582
Hare, Dr. Jonathan P. “The Rough Science Phonograph.” The Creative Science Centre.
http://www.creative–science.org.uk/RS2phono.html
“The Phonograph.” Vintage Audio and Radio. (8/29/02). http://www.audiouk.com/phonograph.htm
“Record Player.” The Columbia Electronic Encyclopedia. Columbia University Press. 2000.
http://www.infoplease.com/ce6/sci/A0841312.html
Saskatchewan Education. “Science 6: Energy in Our Lives.” Science: A Curriculum Guide for the Middle
Level. Regina, SK: Saskatchewan Education. 1993.
http://www.sasked.gov.sk.ca/docs/midlsci/gr6uemsc.html
69
crank
GEORG’S WAVE
WAVES
Visitors set a series of spheres into motion, creating wave patterns along the ceiling.
Text Panel:
Hmm…
- Make the wave move fast and then slow. What differences do you notice?
- What happens to the wave when it gets to the end of the line?
What’s Going On?
The energy you transfer to this connected series of rods and spheres is carried down the line in
the form of a transverse wave.
So What?
So…many kinds of waves share characteristics like frequency, amplitude, and producing echoes.
A single model like this one can be used to show many different things.
Discover More!
- During an earthquake, the ground moves in transverse waves like this and also in
compression waves where the ground is squeezed together then relaxed.
- You can make both types with a Slinky toy. Have a partner stretch the toy out a few feet.
Waving it up and down makes a transverse wave. Pulling together and releasing several
coils makes a compression wave move through the toy.
The BIG Idea: Each particle in a transverse wave moves in a direction that is
perpendicular to the wave’s propagation. The particles do not move along with the wave.
The wave moves through the medium made up of the particles.
Background Information:
A wave is a disturbance that carries energy as it travels (or propagates) through matter or
space. The matter through which the wave travels is called the medium of a wave. Two
types of waves move through matter: transverse waves and longitudinal waves. (Note:
Ocean waves are called orbital waves and are discussed in the “Surf’s Up information.”)
Transverse waves move in such a way that particles making up the medium move back
and forth in a direction that is PERPENDICULAR to the direction of wave propagation.
For example, have two people hold the ends of a rope. One person holds his end of the
rope stationary. The other person
moves her end of the rope up and
down. We would expect to see a
wave propagation
wave moving along the rope between
the two people. The wave moves
along the rope, but any piece of the
rope (see section marked by a black rectangle) moves only up and down. In other words,
the wave moves through the medium and the particles oscillate perpendicular to the
direction of wave propagation.
70
GEORG’S WAVE
WAVES
Anatomy of a Transverse Wave:
crest: the
highest part of
the curve
amplitude: distance from midline to top of
crest or bottom of trough
wavelength, λ:
the distance between two consecutive identical
parts of the wave.
trough: the lowest
part of the curve
Longitudinal waves move in such a way that the particles making up the medium move
side to side in a direction that is PARALLEL to the direction of wave propagation.
To create a longitudinal wave, place a Slinky on a table. Place a volunteer at each end,
holding onto the Slinky.
Have one person quickly push the Slinky straight toward and then (without letting go)
pull the Slinky away from the second person along the table.
wave propagation
The wave will propagate from the person moving the Slinky toward the person holding
the still end. As the wave moves along the Slinky, the Slinky will compress and expand.
Each individual loop of the Slinky will only move side to side a small amount.
The Slinky, itself, does not move along with the wave. The wave moves through the
medium (here, the Slinky) and the particles (the Slinky loops) oscillate side to side,
parallel to the direction of wave propagation.
compression
(area of high pressure)
Anatomy of a Longitudinal Wave
wavelength, λ:
the distance between two
consecutive identical
parts of the wave.
rarefaction
(area of low pressure)
71
GEORG’S WAVE
WAVES
In either case (transverse or longitudinal waves):
•
Each wave cycle consists of one wavelength.
•
The frequency, f, of the wave is equal to the number of wave cycles passing a given
point per second. The unit of measure of frequency is the hertz (Hz) where
1 cycle/second = 1 Hz.
Try this at School:
Slinky in Hand: Making Waves
(Source: Paul Doherty. Science Snacks. The Exploratorium. CA. 1997.
http://www.exploratorium.edu/snacks/slinkyinhand/index.html)
Hold a slinky between your hands; model transverse wave resonances as well as longitudinal
wave resonances. Learn about nodes and antinodes of motion and compression.
materials
- A slinky
- 2 chairs
- about 3 meters of 20 pound test monofilament fishing line: optional substitute for nylon line, a
smooth tabletop
- masking tape
to do and notice
Hold the slinky between your hands. The slinky will be horizontal and sag. Move both of your
hands up and down together. Find the lowest frequency that produces the largest motion of the
slinky for the smallest motion of your hands. (About one cycle per second.) One large hump, half
a wave should appear moving up and down on the slinky. Count the rhythm every time the middle
of the slinky hits bottom, 1,2,3,4,1,2,3,4,... (If you have trouble, try this side to side on a tabletop).
Notice that the center of the slinky moves up and down the most and your hands the least. Move
your hands in opposite directions, that is, move the right hand up when the left hand moves down
and vice-versa. Move them in the same rhythm as above. Notice that your hands move a large
distance whole the center of the slinky hardly moves at all. If you have trouble, try this on a
tabletop.
Count the rhythm every time your right hand hits bottom, 1,2,3,4,1,2,3,4...
what’s going on?
When you move your hands together you make a half-a-wave on the slinky the middle of the
slinky is an antinode, a point of maximum motion while the hand-held ends are nearly nodes,
points of no motion. When you move your hands opposite, a half-a-wave also fits on the slinky.
However, this half wave has one node in the center and two antinodes near the hand-held ends.
The timing on both of these is the same, that is, the period is the same. They both are
resonances in which one-half-wave fits onto the slinky. Both of these patterns of motion have the
fundamental frequency of oscillation, the lowest frequency of motion for a slinky held at both
ends. It is close to 1 hertz.
etcetera
72
GEORG’S WAVE
WAVES
For the transverse motion of the slinky, at places where the motion of the slinky passes through
zero, a node of motion, the slope of the slinky changes the most, an antinode of slope. So, at the
same places where there are nodes of motion, there are antinodes of slope.
assembly
Tie the fishing line to a chair. After the first experiment slide the slinky onto the fishing line then tie
the other end of the fishing line to another chair. Pull the chairs apart until the line is taut.
Optional, rest the slinky on a smooth tabletop. If you use a tabletop, use only 1/2 of a plastic
slinky, otherwise friction will make the experiments difficult.
to do and notice
Thread the slinky onto the monofilament line as described under assembly. Grab the ends of the
slinky in your hands. Stretch the slinky to between 1 and 2 meters long. Move your hands
together and then apart, just as if you were clapping. Notice the motion of the slinky. Your hands
move a lot while the center of the slinky moves very little. The center is a node. You can attach a
small flag of masking tape to the center of the slinky to make it easier to see that the center is not
moving.
Next, notice the spacing between the slinks (turns) of the slinky. When the slinks are jammed
close together the slinky models high pressures in a gas, where the atoms are closer together.
When the slinks are far apart, the slinky models low pressure in a gas. Let’s call closely spaced
slinks high pressure and widely spaced slinks low pressure. Notice that the pressure change is
greatest at the center where the slinks alternately bunch-up and spread apart, and where the side
to side motion of the flag is the least. Count the rhythm of this motion: 1,2,3,4,1,2,3,4... Move both
hands in the same direction, if the slinky stretches right-left move both hands to the left then to
the right. (One of our teachers described this as the sound of one hand clapping twice.)
Notice the motion of the slinky, which is called longitudinal motion. Find the frequency of hand
motion that produces the largest motion of the center of the slinky for the smallest motion of your
hands. Count the rhythm of this motion: 1,2,3,4,1,2,3,4... Notice that the center of the slinky is an
antinode, your hands are nearly nodes. The flag marking the center whips back-and-forth. Notice
that in the center, the slinky moves back and forth but the spacing between the slinks near the
center does not change. The center is an antinode of motion but a node (a place with no change)
of pressure. At the nodes of motion near your hands however the slinks bunch together and then
spread apart: the pressure changes a lot. The hand-held ends are antinodes of pressure. Notice
also that when one hand is at high pressure the other is low. The ends then swap. The highpressure hand becomes a low pressure and vice-versa. In other words, the slinks bunch up near
one hand while they spread out at the other.
what’s going on?
When your hands move together one half wave of longitudinal motion fits on the slinky. This is the
lowest frequency resonance of the slinky held at both ends, it is called the fundamental
frequency. When your hands move opposite, one-half-wave of longitudinal motion also fits on the
slinky but this time the node is in the middle while your hands are near antinodes. A sound wave
is a longitudinal wave. A sound wave can be viewed either as a wave of motion of atoms or as a
wave of pressure. In a standing sound wave in a tube, nodes of motion occur at the same place
as antinodes of pressure. When both of your hands move together and apart as in a normal clap
you are modeling sound waves in a tube closed at both ends. There are motion nodes at the
ends and pressure antinodes. When you move both hands in the same direction, the non-clap,
you are modeling a tube open at both ends. It has motion antinodes at the ends and pressure
nodes.
to do and notice
73
GEORG’S WAVE
WAVES
Find a higher frequency resonance of the longitudinal wave in which you move both hands in the
same direction (anti-clap). You should have to move your hands about twice as often as in the
lowest frequency resonance you created before.
Count the frequency: 1,2,3,4,1,2,3,4. Notice the motion of the slinky, there are two nodes each
about 1/4 of the way from each end. Mark the nodes with flags of masking tape.
One full wave fits on the slinky. When there is a high pressure near one node there is low
pressure near the other. The high-pressure and low-pressure regions switch positions each cycle.
Move your hands opposite each other (clap) and find the next higher resonant frequency.
nodes
|
|
|
There will be three nodes on the slinky, one in the center and the other two, 1/6 of the slinky from
each end. 3/2 of a wave fits on the slinky. Notice the pressure changes on the slinky, when one
node is experiencing high pressure the adjacent one experiences low pressure. With time, each
node oscillates from high pressure to low and back again.
what’s going on?
High-pressure and low-pressure nodes alternate in time as well as in space. To create an odd
number of nodes move your hands opposite each other, clap hands. To create an even number
of nodes move your hands in the same direction.
Visit suggestions/questions:
What happens to the wave when it hits the end of the line of spheres?
Sources:
Anderson, G. “Wave Phenomena: Longitudinal Waves, Transverse Waves and Waves of Mixed Type.” The
Virtual Physics Laboratory. Department of Physics and Astronomy. Northwestern University. Updated
July 10, 2000. (10/18/02). http://www.physics.nwu.edu/ugrad/vpl/index.html
Eby, Denise and Robert B. Horton. Physical Science. NY: Macmillan, 1986.
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Hewitt, Paul B. Conceptual Physics: A High School Physics Program. Menlo Park, CA: Addison Wesley,
1987.
Nave, Carl R. and Brenda C. Nave. Physics for the Health Sciences. Philadelphia: Saunders, 1980.
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
74
LIGHT MIXING
WAVES
Visitors use dimmer switches to change the amounts of overlapping red, blue, and green
light shining on a wall. By standing in front of the spotlights, visitors also create colorful,
multiple shadows.
Text Panel:
Hmm…
- What happens to the screen color if you turn all three lights on or block a light?
- What happens to your clothes under different colored light?
What’s Going On?
Just like mixing paints, mixing three colors of light makes more colors. When you combine all
three primary colors of light – red, green and blue – you get white light.
So What?
So…did you ever notice you might look great in sunlight, but a little ‘green’ under fluorescent
lights in a school or office? How we see colors depends partly on the mixture of the colors in the
light shining on it.
Discover More!
- The primary colors of light are different than the primary colors of paint ( pigment).
Pigments determine color by absorbing some colors and reflecting other back to your eye.
For example, all the colors of light from the sun hit an apple, but only the red color is
reflected off the apple to your eye.
- A red shirt looks black in blue light because there is no red in the light to be reflected back to
your eye.
The BIG Idea:
Colors of light combine differently than color pigments do.
Background Information:
There is a difference between pigment colors and colors of light.
The three primary pigments (paint colors) are red, yellow, and blue. By mixing different
combinations of these colors, all other color pigments can be made.
RED
The secondary pigment colors can be made as follows:
§ Orange = Red + Yellow
§ Green = Yellow + Blue
§ Violet = Blue + Red
Orange
Violet
Green
§
§
Black = all pigments mixed together
White = the absence of all pigment
BLUE
YELLOW
PIGMENT
COLORS
75
LIGHT MIXING
WAVES
The three primary colors of light are red, green and blue. By mixing different
combinations of these colors, all other color of light can be made.
The secondary colors of light can be made as follows:
RED
§ Yellow = Red + Green
Magenta
§ Cyan = Green + Blue
Yellow
§ Magenta = Blue + Red
§
§
White = all colors of light mixed together
Black = the absence of all light
Cyan
BLUE
GREEN
COLORS OF
LIGHT
Try this at School:
Colored Shadows
Make your own version of this popular science center exhibit in a flash.
Use a multi-plug power strip and plug in three colored
bulbs (red, green and blue) in simple socket plugs. Against a white wall
or screen in a darkened room, students can explore subtractive light
mixing – additional colors created by blocking one of the three primary
colors of light.
Visit suggestions/questions:
What do you get when you mix:
blue light + red light ?
red light + green light?
green light + blue light?
blue light + red light + green light?
What color shadow do you have if only the blue light is on?
Turn on two of the colored lights. What color(s) are your shadows? What happens to the color of
your shadows when they cross over each other?
Sources:
“Color Addition and Subtraction.” http://www.uncc.edu/lagaro/cwg/Colors/colorBox1.html
Ellison, Patricia. Colorworm Teaches about Light and Color. 1997.
http://php.iupui.edu/~pellison/colorworm/home.html
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Hewitt, Paul B. Conceptual Physics: A High School Physics Program. Menlo Park, CA: Addison Wesley,
1987.
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
76
LIGHT SITE
WAVES
Visitors explore the properties of light as they experiment with lasers, lenses, white light
and optical fibers.
Text Panel:
Hmm…
- What happens to your hand or a colored shape when you put it on the fiber-optic grid?
- What happens to the beams of laser light and white light when they pass through a lens?
What’s Going On?
Light waves travel in straight lines. The sources of the lights here are either white light or lasers.
Smoked lenses allow you to see how light travels and can be bent.
On the fiber-optic grid, light from one end of each fiber travels to the other end, even when the
fiber is bent.
So What?
So…controlling how light travels and behaves while moving through lenses allows us to make
telescopes, microscopes and binoculars. It also lets doctors perform laser surgery, focusing light
at critical angles to make a cut.
Discover More!
- Feather-weight eyeglass lenses are made of a material which bends the light more through a
thinner lens, making them 30% lighter than regular lenses.
- Improvements in fiber-optic cables let more information, like your voice on the phone or
information on the Internet, be carried more rapidly.
The BIG Idea:
Light can be transmitted, refracted, and reflected.
Background Information:
Transmission and reflection
Fiber optic cables use the principle of internal reflection to transmit light and images. A
fiber optic cable contains bundles of optical fibers. Each optical fiber has a reflective
coating. This allows
light to reflect back
and forth along the
inside of the fiber,
Optical Fiber
even if the cable is
light enters fiber
light exits fiber
gradually curved.
The fibers in this
activity are called
“end-emitting”
optical fibers. End-emitting optical fibers are shielded along their entire length so that
the light that is transmitted escapes (and is visible) only at the end.
77
LIGHT SITE
WAVES
The Light Site table contains adjacent pairs of
large squares covered with small holes. Each hole
in one square is connected with its corresponding
hole in the adjacent square by means of an optical
fiber. An overhead light source shines downward
onto one square in each pair. An opaque object
placed on this square will appear as a dark image
on the other.
The optical
fibers carry the light from one square to the other. If
an opaque object blocks any hole, no light will be
transmitted through the connecting fiber and the
corresponding hole in the adjacent square will
appear dark.
light
source
one optical fiber
Each optical fiber transmits only a fraction of the
image, so the greater the number of holes drilled into the square, the more connecting
optical fibers there are and the better the resolution of the image’s outline is. One can
more easily differentiate the fine detail of the resulting image where there are many fibers
transmitting the image than where there are few fibers transmitting the image.
Refraction
A light wave that is moving from one transparent or translucent medium to another,
bends at the boundary between the two. This bending is called refraction, and it can be
easily seen when a beam of light passes through a prism or a lens.
A lens is a piece of clear plastic or glass with one or more curved surfaces. Light passing
through the lens bends. Optical instruments use lenses, alone or in combination, to
change the way we see. In particular, eyeglasses are used to help people with blurred
vision focus on objects.
Normal vision: The image is focused by the eye’s lens directly on
the retina.
Nearsighted (Myopia): The image is focused in front of the
retina. The eyeball is slightly longer than normal. A nearsighted
person has trouble focusing on objects that are far away.
A diverging lens is used to correct nearsightedness.
Farsighted: (Hyperopia): The image is focused behind the retina.
Either the eyeball is slightly shorter than normal, or the muscles
that control the shape of the lens have weakened. A farsighted
person has trouble focusing on objects that are nearby. A
converging lens is used to correct farsightedness.
78
LIGHT SITE
WAVES
Laser light differs from ordinary, incandescent white light in three basic ways.
1. Wavelength
Laser light is monochromatic.
This means that it is composed
of one wavelength of light.
White light can be broken down into the
entire visible light spectrum because it is
composed of all visible wavelengths of light.
2. Coherence
Laser light is coherent. This means that
all of the light waves are in phase with
one another and are moving in the same
direction.
White light is incoherent. The light waves
interfere with each other because they are
not in phase and are moving in many
directions.
3. Dispersal
A laser beam remains narrow, even at a
great distance from the source.
A beam of white light disperses
(spreads out) as it moves away from
the source.
79
LIGHT SITE
WAVES
Try this at School:
Investigate the differences between white light and laser beams
Materials
- Flashlight
- Cardboard
- Scissors / utility knife
- Masking tape
- Paper
- Prism
- Laser pointer
- Blackboard/ chalk or Whiteboard/ dry-erase marker or paper taped to the wall and a regular
marker
- Spray bottle: e.g. plant mister or empty (clean) hair-spray bottle
Procedure
Using the cardboard, knife, and tape, create a cover for the bulb end of the flashlight such that
the light exits only through a very small hole.
Investigate wavelength composition
- In a dark room, shine the occluded flashlight beam through a prism.
- Observe the refraction of white light.
- Repeat with the laser pointer.
Note: To see the actual beams, use a plant-mister / spray bottle to spray water mist along the
beam paths.
Investigate dispersion
- From a distance of approximately 10 ft away, shine the flashlight onto the blackboard /
whiteboard/ paper and trace around the outer edge of the light circle.
- Repeat using the laser pointer.
Visit suggestions/questions:
Use the lenses to refract a laser beam.
Can you split one laser beam into two beams?
Use a laser beam and the concave and convex lenses to simulate the effect of glasses on vision.
Place a colored shape (or your hand) in the center of one of the fiber-optic squares. How clear is
the transmitted image? Now try placing the same shape on the square so that it partially covers
an edge where there are less optical fibers per inch. How does the clarity of the shape’s
transmitted image change?
Sources:
Hewitt, Paul G. Conceptual Physics, A High School Physics Program. Menlo Park, CA: Addison Wesley,
1987.
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
80
PIAN-O-SCOPE
WAVES
Visitors create visible wave patterns as they play low and high notes on a keyboard
connected to an oscilloscope.
Text Panel:
Hmm…
- What happens to the line on the oscilloscope when you play a note?
- What happens when you hit two very different notes at once?
What’s Going On?
The oscilloscope is a device that can give a visual picture of a sound wave. Higher notes have
more frequent vibrations, making more waves in the same space as a lower note with fewer
vibrations.
So What?
So…by analyzing wave patterns, scientists can discover things about a sound that may be hard to
hear. The image can also be captured to be referred to in later studies.
Discover More!
- The frequency of a wave is the number of crests passing by a fixed point in one second. You
can see on the screen that the higher notes have a greater frequency than lower ones.
- The oscilloscope, invented in 1897, led to the development of television. A proposal to adapt
the simple waveform signal to produce visual images was one of the first steps in the process
that brought “Big Bird” into your living room.
The BIG Idea: The unique sound of a musical instrument is created by the generation of
a particular set of frequencies for each note.
Background Information:
Sound is generated by vibrating objects. A sound is considered to be “noise” when it is
composed of irregular, incoherent vibrations. When a sound results from an object
vibrating at a regular, steady frequency, the sound that is produced may be interpreted as
a musical tone.
When struck, an object will naturally vibrate at a characteristic frequency known as its
fundamental frequency. The pitch (highness / lowness) of a tone depends on this
frequency. Fast moving, high frequency vibrations generate high tones. Slower, low
frequency vibrations generate lower tones.
Electronic frequency generators are able to produce pure tones, each consisting of a
single, fundamental frequency. If all musical instruments generated pure tones, a listener
would be unable to distinguish between one instrument and another. However, objects
may vibrate at more than one frequency at a time.
Musical instruments produce composite sounds with overtones superimposed on the
fundamental frequencies. For any given tone, different types of instruments produce
different numbers of overtones (also known as “harmonics”). Overtones correspond to
multiples of the fundamental frequency.
81
PIAN-O-SCOPE
For example, a
piano string fixed at
both ends, would
naturally vibrate at
the following
frequencies:
WAVES
2nd Overtone
fundamental frequency
While generated at
the same time,
overtones are
produced at a much
lower volume than
1st Overtone
3rd Overtone
the fundamentals. Nevertheless, the overtones are responsible for the timbre (also known
as “tone color” or “quality”) of the tone emitted by an instrument. One way that listeners
can differentiate between instruments is by recognizing the distinctive timbres.
Electronic keyboards are able to reproduce the sounds of different types of instruments
because they are programmed to produce correctly proportioned fundamental frequencies
and overtones corresponding to each instrument’s unique timbre.
Try this at School:
Web site Synthesizer
(Source: Kulesza, Alex, et al. “The Soundry.” A ThinkQuest ’98 entry. (9/18/2000).
http://library.thinkquest.org/19537/Main.html)
Description: The web site listed above provides interactive online experiments dealing with
sound.
One of the interactive experiments: http://library.thinkquest.org/19537/cgibin/showharm.cgi focuses on harmonics (overtones). The user is able to vary the harmonics of a
sound, see the corresponding wave patterns and hear the results. To demonstrate the difference
in timbre between a clarinet and a trumpet, click on the name of each instrument and listen to the
differences.
This is what the user sees on the screen:
Interactive Sound Lab
Harmonic Applet
S
O
U
N
D
1 2 3 4 5 6 7 8 9 10
R
E
S
E
T
Harmonics
82
Pre-Defined
Instruments
CLARINET
TRUMPET
Tunes
TWINKLE
ODE TO JOY
PIAN-O-SCOPE
WAVES
Instructions:
The Harmonics Applet allows you to play with harmonics to produce instrument sounds similar to
the sounds real instruments make. This applet takes the place of an electric synthesizer. The only
difference is that you make the sounds! You can also play songs with the instruments you have
made!
Follow these steps to understand how to use the Harmonics Applet:
1. Click on one of the Pre-Recorded Instrument Sounds that you are familiar with.
2. Notice how the sliders are positioned on each harmonic.
3. Click on the “Sound” button and listen to the synthesized sound of this instrument.
4. Now choose one of the songs and listen to the instrument again.
Press the “Reset” button to bring all the harmonics back to zero. Now, you can start playing with
the harmonics by yourself. To do this, click and hold on one of the sliders and move it up and
down along the harmonic bar. When you decide where to put the slider just let go of the mouse
button and move to the next harmonic. First, you might want to try to copy the harmonics from the
instrument you just heard. Then, when you think you’ve mastered moving the sliders on the
harmonics, create your own instrument! By playing with the controls, you will be able to create
and shape your wave any way you like it. For example, you can create an approximation of a
square wave by setting all of the even harmonics to zero and setting the odd ones at decreasing
levels. Experiment and see what other types of waves you can make. Who knows? Maybe you’ll
stumble upon the sound of another instrument or make a new instrument sound altogether! If you
like what you’ve created, click “Post It!” to share it with others on our message board.
Visit suggestions/questions:
Examine the waves on the screen as you try the following:
Play one note.
Play the same note an octave higher or lower.
Play the two notes together.
Play a bunch of notes at once. What does noise look like on the screen?
Which note produces the longest wavelength? Which produces the shortest wavelength?
Sources:
Apel, Willi, and Ralph T. Daniel. The Harvard Brief Dictionary of Music. NY: Pocket Books, 1961.
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Kulesza, Alex, et. al. “The Soundry.” A ThinkQuest ’98 entry (10/14/02).
http://library.thinkquest.org/19537/
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
“music synthesizer.” Encyclopædia Britannica. Encyclopædia Britannica Inc., 2000.
http://www.britanica.com
“Musical Instruments.” Microsoft® Encarta® Online Encyclopedia. Microsoft Corporation. 2000.
http://encarta.msn.com
“Re: Can I recognize from sound Fourier spectrum a musical instrument?” The MAD Scientist Network.
2000. http://madsci.wustl.edu/posts/archives/oct98/905894507.Ph.r.html
“Re: Relationship of speed or sound, frequency and wavelength.” The MAD Scientist Network. 2000.
http://madsci.wustl.edu/posts/archives/feb98/885616068.Ph.r.html
Serway, Raymond, A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Philadelphia:
Saunders, 1986.
83
RAINBOW
WAVES
A beam of light is split by a prism and projected on a screen, producing a “rainbow.”
Visitors use color filters to modify the projected spectrum.
Text Panel:
Hmm…
- What happens to the colors of the rainbow as different color filters block the light?
- Which colors of light are blocked by which colors of filters?
What’s Going On?
The white light from the bulb is split as it passes through the prism, making a “spectrum” or
“rainbow.” As you change the filter, only the part of the light that is the same color as the filter
is able to pass through.
So What?
So…each type of light – solar, fluorescent bulbs, etc. – have their own individual spectrum.
Scientists can tell what gasses different stars are made from by studying these “fingerprints.”
Discover More!
- The primary colors of light (red, green, blue) are different than the primary colors of paint or
pigment (red, yellow, blue).
- Besides the light you can see here, the bulb also emits invisible waves – like ultraviolet and
infrared. Visit other exhibits in this gallery to explore those wavelengths.
- Put the separated colors of light back together at the “Light Mixing” exhibit in this gallery.
The BIG Idea:
White light moving through a prism refracts and is dispersed, forming a rainbow.
Background Information:
Refraction is the change in direction of a wave as it crosses the boundary between two
media in which it travels at different speeds.
The index of refraction,
speed of light in vacuum
n=
which can be rewritten
speed of light in a medium
as:
n=
wavelength of light in a vacuum
wavelength of light in the medium
incident
ray
Medium 1
Medium 2
Here, the Index of Refraction of Medium 1 is n1 and the
Index of Refraction of Medium 2 is n2
Snell’s Law states that: n1 multiplied by the sine of the
angle of incidence = n2 multiplied by the sine of the angle of refraction
n1 sin(angle 1 ) = n2 sin(angle 2 )
84
angle of
incidence
refracted
ray
angle
of
refraction
RAINBOW
WAVES
Different wavelengths of light travel at different speeds in transparent media. Therefore,
they will refract differently and bend at different angles.
Prisms are pieces of transparent material that are cut
such that they have three flat sides, precise angles, and
two symmetrical ends. As light rays move
from the air into the prism and from the
prism back into the air, they refract.
Because white light is made up of all
wavelengths (and therefore, all frequencies) of visible
light, white light moving through a prism separates out into its components.
The separation of light into colors arranged according to their frequency is called
dispersion.
Try this at School:
How Can You Make a Rainbow Without a Prism?
(Source: Adapted from: Notkin, Dr. Jerome J. et.al. The How and Why Wonder Book of Beginning Science.
NY: Grosset & Dunlap, 1971.)
rainbow
You will use:
Light
- Pan with water
Source
- Mirror
Do this:
- Place a mirror at an angle inside the water-filled pan.
- Place the pan in the path of a strong source of light, near a wall. The rays should strike the
mirror in the water.
- A rainbow should be on the wall.
Why does it work?
As light struck the mirror, it is reflected. However, it is also refracted, or bent, because the rays
pass through more than one substance. The bending light rays separate into their many parts,
each one traveling at a different frequency. The result is the rainbow colors on the wall.
Visit suggestions/questions:
Use the “Rainbow” exhibit to determine how white light can be split apart into its components.
Then go to the “Light Mixing” exhibit and see what happens when you add the blue, red, and
green light back together.
Sources:
Ellison, Patricia. Colorworm Teaches about Light and Color. 1997.
http://php.iupui.edu/~pellison/colorworm/home.html
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Hewitt, Paul B. Conceptual Physics: A High School Physics Program. Menlo Park, CA: Addison Wesley,
1987.
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
85
RIPPLE TANK
WAVES
Visitors use three hand-activated plungers to create waves in a large fluid-filled tank.
The shadows of the waves are projected on the translucent cover of the tank. Three
obstructions inside the tank reflect the waves, allowing visitors to create different types of
interference patterns.
Top view
of tank.
Side View
Text Panel:
Hmm…
- What happens when two waves meet each other?
- What happens when a wave hits an object or the side walls?
What’s Going On?
When waves overlap, they interact with each other to form new patterns. The separate waves add
together in some places and cancel each other out in others. All types of waves (light, sound, and
water) can form interference patterns.
So What?
So…scientists use ripple tanks to study wave movement and patterns.
Discover More
- The frequency of the wave that you create is directly related to your tapping speed. The more
times you depress the plunger per second, the higher the frequency of the wave is.
- The waves in the table reflect off of the tank’s walls and shapes in the center of the table just
like light reflects off of a mirror. The reflected waves form interference patterns with the new
waves you create.
The BIG Idea: When waves traveling in a medium intersect, they form interference
patterns.
Background Information:
When referring to a transverse wave (as shown),
the crest is the highest part of the curve and the
trough is the lowest part. The amplitude is the
distance from the midline to the crest or the trough.
crest
amplitude
amplitude
trough
When two similar waves moving through the same medium meet, they interact with each
other to form an interference pattern. This is true for all types of waves (transverse or
longitudinal). The interference pattern is a combination of the individual waves. Each
wave retains its unique properties, but at any point in the pattern they interact either
constructively or destructively.
86
RIPPLE TANK
WAVES
1
2
Constructive
Interference
2
1
Destructive interference occurs when the amplitude of the
combined waves is smaller than that of either individual wave.
When a crest and trough meet, the crest adds amplitude and the
troughs subtract amplitude from the resulting waveform. If the
magnitude of the crest and trough’s amplitude are the same,
then at the point when they exactly overlap, they will
completely cancel out. As the two waves continue to move in
their original directions and become separate again, their
amplitudes return to their original values.
1
2
Destructive
Interference
2
1
The waves created by the plungers in the ripple tank are circular (like
they would be in the water if a rock were thrown into a pond).
The shadows on the top of the table indicate where the crests are while the light spots on
the table indicate the wave troughs.
shadow on tabletop
actual wave inside of tank
87
Time
For example, two wave crests move toward each other. At the
point when they exactly overlap, their amplitudes add together.
As the two waves continue to move in their original directions
and become separate again, their amplitudes return to their original values.
Time
Constructive interference occurs when the amplitude of the
combined waves is greater than the amplitude of either
individual wave. In other words, if two crests or two troughs
meet, they will form a crest or a trough with an amplitude equal
to the sum of the two combining amplitudes.
RIPPLE TANK
WAVES
Try this at School:
Make your own Ripple Tank
(Source: Adapted from: Elfick, Dr. J. et.al. “Make a Ripple Tank.” New UNESCO Source Book for Science
Teaching Physical Sciences. School of Education, University of Queensland, Brisbane, Australia 1979.
http://www.uq.edu.au/_School_Science_Lessons/UNPhysics.html#Rippletanki)
Materials:
- clear glass baking dish
- water
- clamp
- hacksaw blade
- wire
- overhead projector
- projection screen
- objects to be used as wave barriers
Procedure:
- Place the glass dish on the writing surface of the overhead projector.
- Pour water into the dish so that the water level is approximately ½” deep.
- Attach a piece of L-shaped wire to one end of a hacksaw blade.
- Clamp the hacksaw blade so that the end of the wire dips into the water.
- Turn on the overhead projector.
- Pluck the end of the hacksaw blade and notice the circular waves formed in the water.
- To observe wave reflections, place non-floating objects that are taller than the water level in
the tank.
Visit suggestions/questions:
Slowly turn the barriers in the center of the table so that they are facing a different direction. Wait
for the liquid to settle down and create a wave that moves toward the barriers. How does the
shape of the edge affect the waves’ reflections?
Turn the knobs back and forth quickly. Look at the wave turbulence created in the table. What
happens to the liquid near the edges of the shapes?
Sources:
Anderson, G. “Wave Phenomena: Reflection of Waves.” The Virtual Physics Laboratory. Department of
Physics and Astronomy. Northwestern University. Updated July 10, 2000. (10/18/02).
http://www.physics.nwu.edu/ugrad/vpl/waves/wavereflection.html
Christian, Wolfgang. “Physlet Animation: two in-phase point source interference.” webphysics. 1998.
http://online.cctt.org/physicslab/content/applets/interference/physlet.htm
Falstad, Paul. “Ripple Tank Simulation.” Java Applet 2001. http://www.falstad.com/ripple/index.html
Hecht, Eugene. Optics. 2nd ed. Reading, MA: Addison-Wesley. 1987.
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
“Reflection and Passing of a Single Wave.” Computer Animations of Physical Processes. Siltec Ltd. 2002.
http://www.infoline.ru/g23/5495/Physics/English/waves.htm
Renault, Pascal. “Wave interference.” This applet illustrates the principles of constructive and destructive
interference of transverse waves. 2000. http://users.erols.com/renau/wave_interference.html
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
Surendranath. B. “Interference in a Ripple Tank.” Java Applet.
http://surendranath.tripod.com/Interference/Ripint.html
88
ROCK MUSIC
WAVES
Visitors hear and feel the vibrations they create as they play a xylophone made of
different lengths of geologic core samples.
Text Panel:
Hmm…
- Which cores make higher sounds?
- What do you feel if you touch a core while you strike it?
What’s Going On?
When you strike one of these rock cores, you make its molecules vibrate. Every object has a
natural vibration; the shorter the core, the faster the vibrations repeat and the higher the pitch.
So What?
So…vibrations like these are the source of all sound in our world. Vibrations can be caused by
plucking strings (guitars), hitting a flexible surface (drums), blowing air (horns) or muscles
contracting (your voice!).
Discover More!
- If these cores were colder, their pitch would be higher. Cold objects contract, making the
molecules closer, so the sound wave travels faster.
- You can make an instrument by filling glass bottles with different amounts of water. Then
strike them with a pencil to hear the tone they make as the glass vibrates. You get a different
tone if you blow across the top, vibrating the air inside.
- A house fly buzzes in the key of ‘F.’
The BIG Idea: The pitch of the sound produced by a vibrating rod is proportional to the
rod’s length.
Background Information:
Sound is generated by vibrating objects. A sound is considered to be “noise” when it is
composed of irregular, incoherent vibrations. When a sound results from an object
vibrating at a regular, steady frequency, the sound that is produced may be interpreted as
a musical tone.
When struck, a rod or bar will naturally vibrate at a characteristic frequency known as its
natural, fundamental frequency. This frequency is determined by the object’s material
properties and is inversely proportional to the wavelength, λ, of the vibration.
The frequency of a sound equals the speed of the sound moving through a medium
divided by the wavelength of the sound.
v
f=
λ
Therefor, the relationship between the frequency and wavelength is an inverse one. The
longer the wavelength, the lower the frequency. The shorter the wavelength, the higher
the frequency.
89
ROCK MUSIC
WAVES
The pitch (highness / lowness) of a tone depends on the vibrating rod’s fundamental
frequency. Fast moving, high frequency vibrations generate high tones. Slower, low
frequency vibrations generate lower tones.
The wavelength of the vibration is directly related to the length of the rod that is being
struck. For example,
L
Rods 1 and 2 are fixed
through their centers to a
cross bar.
Rod 1
λ 1 = 2L
The length of Rod 1 is
equal to L. If Rod 1 is
struck, the wavelength, λ1 , of the resulting vibration is equal to two times the length of
v
the rod, or 2L. The frequency of this vibration will be f1 = =
λ1
½L
v
2L
Rod 2
The length of Rod 2 is equal to ½L (it is half as long as Rod 1).
If Rod 2 is struck, the wavelength, λ2 , of the resulting vibration
is equal to two times the length of the rod, or L. The frequency of this
v
v
v
vibration will be f2 =
= = 2x
= 2f1
λ2 L
2L
λ2 = L
This means that the frequency of the vibration in Rod 2 is twice as fast as the frequency
of the vibration in Rod 1. Therefore, the pitch of the sound being generated by Rod 2
will be higher than that of the sound being generated by Rod 1.
The shorter the rod, the higher the sound that is generated when the rod is struck.
Try this at School:
Coat Hanger Bell
Materials:
- string
- metal coat hanger
- table
Procedure:
- Tie a string to each end of an inverted metal coat hanger, and wrap the other end around your
fingers.
- Lightly place your fingers in your ears, then knock the coat hanger into a table or chair.
- Vary the objects (different kinds of hangers, spoons, forks), kinds of string and length of string.
- Describe how the sound changes.
Energy from the vibrating molecules in the object gets transferred to the string, which acts like a
funnel to keep all the sound energy traveling to your ear, rather than letting it spread out in the air.
When you strike an object it will vibrate at its natural frequency. Each object will create a different
pitch. Longer strings produce lower notes because they have fewer vibrations.
90
ROCK MUSIC
WAVES
Visit suggestions/questions:
Explore the relationship between the length of the rods and the sounds that you hear.
Try feeling the vibrations of the rock cores as you hit them with the mallets. Can you feel
differences between the vibrations of the longest core and the shortest?
Sources:
“Lesson 4: Resonance and Standing Waves: Natural Frequency.” The Physics Classroom, A High School
Physics Tutorial. The Physics Classroom and Mathsoft Education & Engineering, Inc. 2002. (7/29/02).
http://www.physicsclassroom.com/Class/sound/U11L4a.html
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin, 1988.
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
91
SHADOW CATCHER
WAVES
Visitors view objects under white light and then ultraviolet light and observe how the
type of light changes the objects’ appearances.
Text Panel:
Hmm…
- Can you tell which objects will glow under the ultraviolet light?
- Which objects change under UV light? Which remain the same?
What’s Going On?
Some of these objects contain elements that absorb ultraviolet radiation and release that energy
in the form of visible light.
So What?
So…ultraviolet radiation has dozens of uses in our lives, from killing bacteria on food to making
bar codes visible to computer scanners at the post office. It’s also the radiation that tans, and
burns, your skin!
Discover More!
- Some objects continue to glow for a time after the UV radiation is taken away. This process
is called fluorescence, and occurs as the electrons affected by the radiation settle back into
place.
- Many detergents have fluorescent material added “to make your whites look whiter!” The
real reason they look “whiter” is that they are reacting to the UV radiation present in the
white light of the sun.
The BIG Idea: Although ultraviolet light is an invisible form of electromagnetic
radiation, its effects on objects are sometimes visible to the human eye.
Background Information:
The Electromagnetic (EM) Spectrum is a continuous range of waves; each made up of
electric and magnetic fields. As they travel, these waves carry energy. The energy
carried by a wave depends on its wavelength. All EM waves travel at a speed of 3.0x108
m/s (the speed of light) in a vacuum. Visible light is the part of the EM spectrum that
normal human eyes can detect. Of the visible spectrum, red light has the longest
wavelength and violet light has the shortest.
The Electromagnetic Spectrum
RADIO
104 102
MICROWAVE
1
INFRARED
10-3
VISIBLE ULTRAVIOLET X-RAY GAMMA RAY
10-5
(Wavelength in Meters)
92
10-6
10-7 10-10 10-12
SHADOW CATCHER
WAVES
Waves that have a slightly shorter wavelength than the visible violet waves are called
ultraviolet (UV) radiation. Although UV radiation constitutes only about five percent of
the total energy emitted from the sun, it is the major energy source for the stratosphere
and mesosphere, playing a dominant role in both energy balance and chemical
composition. Most UV radiation is blocked by the Earth’s atmosphere, but some solar
UV penetrates and aids in plant photosynthesis and helps produce vitamin D in humans.
Too much UV radiation can burn the skin, cause skin cancer and damage vegetation.
A black light primarily emits UV radiation.
A sealed glass tube is filled with a lowpressure inert gas (typically Argon) and a small amount of liquid Mercury. Two
electrodes are attached, one at each end of the tube. When these electrodes are connected
to an ac circuit, a voltage differential is created across the electrodes. As the electrical
current alternates, the electrons in the gas migrate from one end of the tube to the other.
The energy in the bulb changes some of the liquid Mercury into Mercury gas.
When the gaseous Mercury atoms collide with the electrons moving through the tube, the
atoms’ level of energy increases. The Mercury atoms’ electrons move to higher energy
states and upon returning to their ground states, they emit photons in the ultraviolet range.
Some objects “fluoresce” under black light. The highly energetic photons emitted by the
black light collide with atoms in the object, heat the object, and excite the electrons in its
atoms. When the electrons fall back to lower energy states, they release more photons.
The photons released by the object have less energy, and therefore longer wavelengths,
than the photons that initially collided with it. The newly released photons are in the
visible range, so the object glows. The type of atomic elements that make up the material
determines the color of the glow.
Try this at School:
Detecting Things We Cannot See: Learning the Concepts of Control and Variable in an Experiment
(Source: Brook-Dupree, Anita. Sciencelines: A Newsletter from the Teacher Resource Center at Fermilab
(An Alternative Middle Years School in Philadelphia, PA). Updated: August 4, 1997.
www-ed.fnal.gov/trc/sciencelines_online/activities.html)
Grade level: K-8th grade
Objectives:
1. Students will make a simple Sunprint and learn the term “control” as used in an experiment.
2. Students will generate a list of variables, learn the term “variable,” and test one of the
variables.
Materials:
- Sunprint paper: Sunprint paper can be purchased inexpensively at various science museum gift shops
or directly from the manufacturer: The Lawrence Hall of Science, University of California at Berkeley,
Berkeley, CA 94720(510) 642-1016 FAX (510) 642-1055
-
Various objects to be used to make prints
93
SHADOW CATCHER
WAVES
Procedure (2 class periods)
First do a basic Sunprint with the students. This will serve as the control. Put the term “control”
on the board and discuss the term control before you start. Tell the students that this is the print
with which other prints will be compared. The directions for a basic Sunprint are on the package
of Sunprint paper that you will need to purchase to do this activity.
1. Select an item such as a key, leaf, or a paper cut out of a heart, or the student's initials.
2. Assemble the parts of the Sunprint kit in this order: a piece of cardboard, Sunprint paper blueside up, item, acrylic sheet.
3. Expose this assembly to the sun until the paper turns almost white. This may take from 1-5
minutes, depending on the sunlight. Try not to over expose the Sunprint paper.
4. Quickly rinse the Sunprint paper in a tub of water for about one minute. Dry the print flat.
Students may want to frame their Sunprints with construction paper. Save all the Sunprints so
they can be compared to the prints done during the next class period.
During the next class period have students think in terms of variables. Put the word “variable” on
the board and explain that this is the thing that will change. Have students brainstorm ideas to
turn this art activity into an experiment. I have students write ideas about what they could
change. These variables can be tested and the changes may be observable on the paper. I
encourage students to think like scientists. A list of variables might look like this: use
incandescent light bulbs of various wattage, use fluorescent bulbs, conduct the experiment in the
shade, coat the acrylic plate with sunscreens of various SPF prior to exposing in the sun
The list can, and will go on and on with the teacher's help. Students love to write on the board,
so I usually have a recorder write the ideas as they come in from the groups of four. After the list
has been generated, students may choose a variable. Every one gets Sunprint paper in a black
envelope and an opportunity to do the experiment. My favorite variable is the use of sunscreens
on the acrylic plate using different SPF. The results are quite dramatic.
Background Information:
Sunprint paper is sensitive to UV light. Ultraviolet light, invisible to our eyes, is a higher energy
type of light than the visible light that we ordinarily see. Sunprint paper absorbs ultraviolet light.
Ultraviolet light causes a chemical change in the paper, which changes the color from blue to
white. The energy from ultraviolet light is what causes the chemical make-up of the paper to
change. Water reacts with the unexposed Sunprint paper (paper covered by an object) changing
the color to white.
Opaque objects that do not allow any UV light to pass will result in white areas on the Sunprint
paper. Objects that allow UV light to pass will result in dark blue areas. Translucent objects, like
a leaf or a crystal, will allow some UV light to pass, causing the paper to partially react.
Visit suggestions/questions:
Try to identify all of the objects in the “See UV” table.
Before the buttons are pressed, predict what will happen to the appearance of the objects when
the black lights are turned on. Press the button and hold it down. Were the predictions accurate?
Do the clothes that you are wearing (particularly white articles) glow under the black light? Why?
Sources:
Harris, Tom. “How Fluorescent Lamps Work.” How Stuff Works. Howstuffworks, Inc. 2002.
http://www.howstuffworks.com/fluorescent-lamp.htm
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Hewitt, Paul B. Conceptual Physics: A High School Physics Program. Menlo Park, CA: Addison Wesley, 1987.
Sonntag, Mark. The Nature of Light, Physics Department, Angelo State University, San Angelo, TX.
(8/1/02). http://quark.angelo.edu/~msonntag/physics1301/electromagneticspectrum.htm
94
SHADOW CATCHER
WAVES
Visitors strike a pose in front of a phosphorescent wall. A spotlight flashes on and off
and the visitors’ “frozen” shadows remain on the wall for several seconds.
Text Panel:
Hmm…
- Try standing close then far away from the wall.
- What happens to the size of your shadow?
- What happens when you wave your arm?
What’s Going On?
The wall is made up of material that absorbs and gives off energy. When the spotlight shuts off,
the wall continues to emit light. In places where you block the spotlight, the wall stays dark.
So What?
So…this type of material is used on emergency exits and directional signs. If power in a building
goes out, you are still able to see the glow of the signs.
Discover More!
- The wall material contains phosphorescent chemicals. Things that are phosphorescent have
the ability to store light energy and release it gradually over a period of time.
- Phosphorescence is not the same as fluorescence. Fluorescent materials only glow while
under ultraviolet (or ‘black’) light. See the “See UV” exhibit for examples of fluorescent
materials.
The BIG Idea:
Phosphorescent materials release stored energy, in the form of
visible light, over time.
electron in its
ground state
Background Information:
An atom consists of a nucleus (containing protons and
neutrons) and electrons, which orbit its nucleus.
1)
The level of energy that an atom has at any given time is
called its energy level or state. When an atom has the lowest
amount of energy that it can possible have, it is said to be in its
ground state. Its electrons are in their ground state orbits.
2)
When energy is added to the atom, its electrons move to
higher energy orbits. The atom becomes excited.
3)
The atom cannot remain in an excited state indefinitely.
Eventually, the electrons release their extra energy in the form
of photons (little packets of light), and the electrons fall back
to their ground states. This may be a multi-step process – the
electrons may release a portion of their energy, pause at an
intermediate orbit, and then release the remainder of their
energy at a later time.
95
nucleus
ENERGY
electron in
an excited
state
electron in a lower
excited state
photon
electron back at
its ground state
4)
photon
SHADOW CATCHER
WAVES
The speed at which electrons return to their ground states, determines whether a material
is considered fluorescent or phosphorescent.
In a fluorescent material, the electrons return to their ground states quickly (in less than a
tiny fraction of one second). Once the energy source is removed, the material no longer
emits light.
In a phosphorescent material, the electrons may not return to their ground states for
several seconds, minutes, hours or even days. That is why it continues to emit light after
the energy source is removed.
The Shadow Catcher wall is covered with a type of vinyl that contains phosphorescent
particles mixed together with a fluorescent dye. The phosphorescent particles absorb the
spotlight’s electromagnetic radiation and begin emitting a pale blue visible light. The
energy of these blue photons in turn excite the fluorescent particles, which immediately
emit bright green light. This is the reason that the wall has a greenish glow.
When you stand in front of the Shadow Catcher, your body blocks the spotlight’s energy
from reaching portions of the wall. The atoms in the parts of the wall that correspond to
your shadow do not absorb electromagnetic energy, do not become excited, and
therefore, do not emit visible light. The remainder of the wall absorbs energy and emits
light around your shadow (which remains dark). That is why you can still see your
shadow when you step away from the wall.
Try this at School:
Fluorescent probing
(Source: Modified from: Doherty, Paul. “Scientific Explorations with Paul Doherty.” June 25, 1999.
http://isaac.exploratorium.edu/~pauld/activities/fluorescence.html)
Introduction
Use a black light to examine the fluorescence from everyday materials.
Materials
- A "Black Light" (ultraviolet lamp)
- fluorescent minerals such as fluorite, calcite and ruby. (available from mineral shops.)
- Liquid Tide (or many other premium liquid laundry detergents.)
- quinine water
- fluorescent plastic
- phosphorescent toys (glow in the dark)
To Do and Notice
- Turn off the room lights, notice that the "glow-in-the-dark” objects continue to glow - they are
phosphorescent.
- Use the black light in a dark room to search for fluorescent objects. Look at white clothing,
white paper, teeth, minerals, liquid tide and quinine water. The glow that emanates from
some of these objects is fluorescence.
- A simple test to separate phosphorescence from fluorescence is to simply turn off the black
light. If an object continues to glow it is phosphorescent, if the glow goes out instantly it is
fluorescent.
96
SHADOW CATCHER
-
-
WAVES
Liquid detergents such as Tide contain a colorless dye that absorbs ultraviolet and produces a
blue fluorescence. In a dark room, shining a black light on a detergent will cause a brilliant
blue glow.
A ruby will fluoresce red when exposed to ultraviolet light if the ruby has no iron impurities.
The red light is the same light produced by a ruby laser.
Quinine water will glow a weird blue. Drinking quinine water illuminated by black light will really
entertain an audience. See Eddie Murphy in the nutty professor for example!
Change the temperature of the phosphorescent materials by holding them over hot water or
blowing on them with the hot air of a hairdryer. Notice that heating causes them to glow more
brightly.
Heat the fluorescent materials. Notice that their temperature does not affect the amount of
light they emit.
What’s Going On?
- A simple definition of fluorescence is that it is light emitted by an object excited by light, where
the emitted light is of a different color, i.e. lower energy, than the exciting light, and where the
emitted light stops immediately after the exciting light is turned off. The light will turn off in as
little as 10-8 seconds.
- In phosphorescence, on the other hand, light continues to be emitted after the exciting light is
turned off. The light will continue to be emitted for seconds or even hours.
- A more advanced definition of phosphorescence is that it is temperature-dependent while
fluorescence is independent of temperature. Hot phosphorescent objects will glow more
brightly for a shorter time than cold ones.
Etc.
It is a cultural phenomenon that we in the United States correlate cleanliness with the bluish white
appearance of white fabrics. Detergent manufacturers know this and add a colorless dye to the
liquid detergents. This dye absorbs ultraviolet and emits blue light. This is a cultural phenomenon
and is not true throughout the world. A typical fluorescent brightener for North American laundry
detergent is: 1,4-bis(styryl) benzene.
References:
The Physics and Chemistry of Color, by Kurt Nassau, Wiley, NY, 1983
Visit suggestions/questions:
-
Do all materials block the light from reaching the shadow wall in the same way?
What happens if you place a pair of regular eyeglasses in front of the wall?
What happens if you place a pair of sunglasses in front of the wall?
What happens if the sunglasses are polarized? Does it change the result?
Sources:
Adam, Harry. “Re: How do you make a shadow wall?” The MAD Scientist Network. 2000. (10/15/02).
http://madsci.wustl.edu/posts/archives/feb2001/983369249.Ph.r.html
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
“How does glow-in-the-dark stuff work?” How Stuff Works. Howstuffworks, Inc. 2002. (10/15/02).
http://www.howstuffworks.com/question388.htm
“Phosphorescence.” Encarta World English Dictionary. Microsoft Corporation. 2001.
Sieber, Werner. “Re: Why does the TV stay bright after you put a flashlight onto it?” The MAD Scientist
Network. 1997. (10/15/02). http://madsci.wustl.edu/posts/archives/mar97/857701589.Ph.r.html
97
SHADOW CATCHER
WAVES
Starr, Jeremy. “Re: How do glow-in-the-dark stickers glow?” The MAD Scientist Network. 1998.
(10/15/02). http://madsci.wustl.edu/posts/archives/may98/895290029.Ch.r.html
“Things that Glow in the Dark.” The Institute for Chemical Education. Madison, WI. Updated 7/11/99.
(10/15/02). http://ice.chem.wisc.edu/materials/light/lightandcolor6.html
98
SURF’S UP
WAVES
Visitors recreate ocean waves by tipping a six-foot-long tank filled with two liquids.
Crests, troughs, frequency and wave patterns can all be observed by tipping the tank.
Text Panel:
Hmm…
- What happens to a wave when it hits the other side of the tank?
- What happens when two waves from opposite ends of the tank meet in the middle?
What’s Going On?
There are two liquids of different density in this tank, one floating on top of the other. The
friction of the liquids sliding past each other makes waves which crest as they hit the slope of the
tank.
So What?
So…we actually live at the bottom of an ocean of air! Air and water are liquids, one floating on
top of the other. In a body of water, waves are formed as the wind pushes the water along.
Discover More!
- Waves can also be created by the energy released from underwater earthquakes. These are
called tsunamis, and can be as high as 90 feet (30 meters)!
- The forces at work in this tank are the same ones that help give Jupiter its distinctive rolling
bands of clouds.
- The energy of waves on the shore is a factor in erosion of the land.
The BIG Idea:
While an ocean wave travels through water, the individual water molecules do not travel
along with the wave.
Background Information:
Waves on the open ocean are typically formed when wind blows across the surface of the
water.
The size of a wave is influenced by three variables:
Variable
Definition
Unit
Conversion to
Conventional Units
Conversion to
SI Units
Wind
Speed
speed of wind
knot
1.151 mph / knot
1.852 kph / knot
distance traveled by a wave with
no obstruction
length of time that the wind has
blown in the same direction
1 Nautical
Mile (nm)
1.151 miles / nm
1.852 km/ nm
Fetch
Duration
hours
Ocean waves that occur at the boundary between air and water or between layers of
liquid with different densities are called orbital waves. As the wave moves along the
water, the water particles move in closed loops.
99
SURF’S UP
water particle
WAVES
wave direction
Source: Modified from: Witenstein, Ben, Introduction to Energy Extraction from Gravity Waves. January
6, 2002. (10/18/02).
http://gore.ocean.washington.edu/fluids/fluids99/student_pages/witenstein/introduc.htm
This type of wave is also called a progressive wave, because the wave moves forward in
one direction.
Try this at School:
Wave Bottle: Make your own Surf’s Up! Exhibit
Materials:
- a clear one-liter plastic bottle with tight-fitting cap
- water
- food coloring (any color)
- mineral or cooking oil (Note: if you plan to keep your wave bottle for a while, use mineral oil –
cooking oil is likely to become rancid).
- funnel
Procedure:
- Clean the plastic bottle thoroughly. Make sure not to leave any soap residue in the bottle.
- Using a funnel, fill the bottle 1/2 full of water. Add a few drops of food coloring to the water.
- Using the funnel, fill the rest of the bottle with mineral oil.
- Replace the cap on the bottle; make sure that it is as tight as possible.
- Hold the bottle upside-down over a sink to make sure that it does not leak.
- Clean any oil off the outside of the bottle with soapy water.
- Make waves!
Background Information:
Density is a measure of a material’s “compactness” and is defined to be the ratio of mass to unit
volume. A material in which the molecules are closely packed together is more dense than a
material in which the molecules are spread apart.
When non-reactive fluids (liquids or gasses) of different densities are mixed together in a
container, the fluids will eventually separate. The fluid with the greater density will sink to the
bottom of the container, while the fluid that is less dense will float to the top.
Visit suggestions/questions:
Slowly tilt the wave box so that one end is at its lowest point.
Watch the wave that you’ve created move through the box.
Tilt the wave box so that one end moves from its lowest to highest to lowest point.
What happens to the waves inside?
100
SURF’S UP
WAVES
Sources:
“Animation: The Wave Machine.” Savage Seas. PBS Online.
http://www.pbs.org/wnet/savageseas/multimedia/wavemachine.html
Dalrymple, Robert A. “Velocities Under Water Waves.” Center for Applied Coastal Research. University
of Delaware. February 17, 1999. (10/18/02). http://www.coastal.udel.edu/faculty/rad/linearplot.html
Garrison, Tom. Oceanography: An Invitation to Marine Science. Wadsworth, Inc. Belmont, CA: 1993.
O’Brien, Thomas, Stannard, Carl and Andrew Telesca. “A Baker’s Dozen of Discrepantly Dense Demos.”
Science Scope. October 1994. pp. 35-38.
“Orbital Motion.” (animation). Lecture Stuff and Handouts – Index. Introduction to Oceanography.
Geoscience 110. Winona State University. April 8, 2002. (10/18/02).
http://www.winona.msus.edu/geology/oceanography/Handouts/index.htm
101
THERM-O-VISION
WAVES
Visitors see the heat from their bodies and the surrounding area when they stand in front
of an infrared camera and a 60-inch television screen.
Text Panel:
Hmm…
- What parts of your face are the hottest (lightest color on this screen)?
- Can you make part of your face or hands hotter?
What’s Going On?
You are looking at an infrared image of yourself. The camera sees only the invisible heat
radiating from you and this room, and shows the different temperatures as different colors.
So What?
So…seeing the normally unseen world can tell us quite a bit. We can learn where an engine is
running the hottest, where heat is escaping from our homes, or even who might have a fever!
Discover More!
- Farmers are using infrared satellite images of their fields to determine if they need to water
the crops or spray for insects.
- Fire departments are beginning to equip firefighters with infrared cameras that let them see
through dense smoke and find the fire – or you!
The BIG Idea: Infrared radiation is the invisible part of the electromagnetic spectrum
that we experience as heat energy.
Background Information:
The Electromagnetic (EM) Spectrum is a continuous range of waves; each made up of
electric and magnetic fields. As they travel, these waves carry energy. The energy
carried by a wave depends on its wavelength. All EM waves travel at a speed of 3.0x108
m/s (the speed of light) in a vacuum. Visible light is the part of the EM spectrum that
normal human eyes can detect. Of the visible spectrum, red light has the longest
wavelength and violet light has the shortest.
The Electromagnetic Spectrum
RADIO
104 102
MICROWAVE
1
INFRARED VISIBLE ULTRAVIOLET X-RAY GAMMA RAY
10-3
10-5
10-6
10-7 10-10 10-12
(Wavelength in Meters)
Waves that have a slightly longer wavelength than the visible red waves are called
infrared radiation (IR). We experience infrared radiation as heat.
102
THERM-O-VISION
WAVES
A thermal camera is a device that senses heat emitted by surrounding objects and creates
an electronic thermal “map” of the same area. The detected temperature range is
translated into a visible color spectrum so that the previously invisible infrared readings
can be viewed on a video monitor.
Try this at School:
Herschel Infrared Experiment
(source: Hermans -Killam, Linda. “Activities and Experiments.” The Space Infrared Telescope Facility, Jet
Propulsion Laboratory, NASA. June 18, 2001. http://sirtf.caltech.edu/EPO/Herschel/experiment.html)
Purpose / Objective: To perform a version of the experiment of 1800, in which a form of radiation
other than visible light was discovered by the famous astronomer Sir Frederick William Herschel.
Background: Herschel discovered the existence of infrared light by passing sunlight through a
glass prism in an experiment similar to the one we describe here. As sunlight passed through the
prism, it was dispersed into a rainbow of colors called a spectrum. A spectrum contains all of the
visible colors that make up sunlight. Herschel was interested in measuring the amount of heat in
each color and used thermometers with blackened bulbs to measure the various color
temperatures. He noticed that the temperature increased from the blue to the red part of the
visible spectrum. He then placed a thermometer just beyond the red part of the spectrum in a
region where there was no visible light -- and found that the temperature was even higher!
Herschel realized that there must be another type of light beyond the red, which we cannot see.
This type of light became known as infrared. Infra is derived from the Latin word for "below."
Although the procedure for this activity is slightly different than Herschel's original experiment,
you should obtain similar results.
Materials: One glass prism (plastic prisms do not work well for this experiment), three alcohol
thermometers, black paint or a permanent black marker, scissors or a prism stand, cardboard box
(a photocopier paper box works fine), one blank sheet of white paper.
Preparation: You will need to blacken the thermometer bulbs to make the experiment work
effectively. One way to do this is to paint the bulbs with black paint, covering each bulb with about
the same amount of paint. Alternatively, you can also blacken the bulbs using a permanent black
marker. (Note: the painted bulbs tend to produce better results.) The bulbs of the thermometers
are blackened in order to absorb heat better. After the paint or marker ink has completely dried on
the thermometer bulbs, tape the thermometers together such that the temperature scales line up
as in Figure 1.
Figure 1
103
THERM-O-VISION
WAVES
Procedure: The experiment should be conducted outdoors on a sunny day. Variable cloud
conditions, such as patchy cumulus clouds or heavy haze will diminish your results. The setup for
the experiment is depicted Figure 1. Begin by placing the white sheet of paper flat in the bottom
of the cardboard box. The next step requires you to carefully attach the glass prism near the top
(Sun-facing) edge of the box.
If you do not have a prism stand (available from
science supply stores), the easiest way to mount the
prism is to cut out an area from the top edge of the
box. The cutout notch should hold the prism snugly,
while permitting its rotation about the prism's long axis
(as shown in Figure 2). That is, the vertical "side" cuts
should be spaced slightly closer than the length of
the prism, and the "bottom" cut should be located
slightly deeper than the width of the prism. Next,
slide the prism into the notch cut from the box and
rotate the prism until the widest possible spectrum
appears on a shaded portion of the white sheet of paper at the bottom of the box.
Set-Up:
1
2
3
4
The Sun-facing side of the box may have to be elevated (tilted up) to produce a sufficiently wide
spectrum. After the prism is secured in the notch, place the thermometers in the shade and
record the ambient air temperature. Then place the thermometers in the spectrum such that one
of the bulbs is in the blue region, another is in the yellow region, and the third is just beyond the
(visible) red region (as in Figure 3).
104
THERM-O-VISION
WAVES
Figure 3
It will take about five minutes for the temperatures to reach their final values. Record the
temperatures in each of the three regions of the spectrum: blue, yellow, and "just beyond" the
red. Do not remove the thermometers from the spectrum or block the spectrum while reading the
temperatures.
Data / Observations:
Thermometer #1
Thermometer #2
Thermometer #3
Temperature in
the shade
Temperature in
the spectrum
Thermometer #1
(blue)
Thermometer #2
(yellow)
Thermometer #3
(just beyond red)
After 1 minute
After 2 minutes
After 3 minutes
After 4 minutes
After 5 minutes
Note: Depending on the position of the prism relative to the Sun, the colors of the spectrum may
be reversed from what is show in the figures.
Questions: What did you notice about your temperature readings? Did you see any trends?
Where was the highest temperature? What do you think exists just beyond the red part of the
spectrum? Discuss any other observations or problems.
105
THERM-O-VISION
WAVES
Remarks to the Teacher: Have the students answer the above questions. The temperatures of
the colors should increase from the blue to red part of the spectrum. The highest temperature
should be just beyond the red portion of the visible light spectrum. This is the infrared region of
the spectrum. Herschel's experiment was important not only because it led to the discovery of
infrared light, but also because it was the first time that it was shown that there were forms of light
that we cannot see with our eyes. As we now know, there are many other types of
electromagnetic radiation ("light") that the human eye cannot see (including X-rays, ultraviolet
rays and radio waves). You can also have the students measure the temperature of other areas
of the spectrum including the area just beyond the visible blue. Also, try the experiment during
different times of the day; the temperature differences between the colors may change, but the
relative comparisons will remain valid.
For further information on the Herschel infrared experiment see:
http://sirtf.caltech.edu/EPO/Herschel/herschel.html
For further information on Infrared and Infrared Astronomy see:
http://www.ipac.caltech.edu/Outreach/Edu/
If you wish to have your results posted online you may send them to outreach@ipac.caltech.edu
Visit suggestions/questions:
Stand in front of the Therm-O-Vision screen.
Which colors correspond with the warmest temperatures? Which colors correspond with the
coolest temperatures?
Which part of your face is the warmest?
Spread your fingers apart and place your hands on your stomach. Keep your hands in one place
for about 15 seconds. Now let go and look at your stomach on the screen. What happened?
Watch the screen. What happens to the color of your hands if you rub them together quickly?
Stand so that you can see your feet on the screen. Rub your feet on the carpet (like you were
trying to wipe mud off the bottom of your shoes). Look at the floor on the screen. Look at the
image of the bottom of your shoe. What happened?
What is the temperature like inside of your mouth?
What happens if you are wearing glasses?
Sources:
Hermans-Killam, Linda. Infrared Astronomy. IPAC (the Infrared Processing and Analysis Center) and
The National Aeronautics and Space Administration (NASA)’s Infrared Astrophysics Data Center.
operated by the California Institute of Technology, Jet Propulsion Laboratory under contract NASA.
Updated: 7/9/02.
http://www.ipac.caltech.edu/Outreach/Edu/
Sonntag, Mark. “The Nature of Light.” Physics Department. Angelo State University. San Angelo, TX.
(8/1/02). http://quark.angelo.edu/~msonntag/physics1301/electromagneticspectrum.htm
Tyson, Jeff. “How Night Vision Works.” How Stuff Works. Howstuffworks, Inc. 2002.
http://www.howstuffworks.com/nightvision.htm
106
NATIONAL SCIENCE CONTENT STANDARDS
Surf's Up
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Therm-O-Vision
x
See UV
x
Shadow Catcher
Rock Music
Ripple Tank
Rainbow
Pian-O-Scope
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
107
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Light Site
x
x
x
x
Light Mixing
x
Georg's Wave
Echo Tube Tube Tube
x
Edison Phonograph
Audio Visible / Visible Vibes
Wild Winds
Wheel of Disaster
Volcano!
What's Shakin'?
Twister!
Hurricane!
Seismic Waves
Earthquake Café
Aeolian Landscape
Wing It!
Walk-in Wind Tunnel
x
x
Roll Pitch Yaw Plane
Drag Race
x
x
In-flight Movies
Bernoulli "AIR"
Convection Currents
K-4
B: Physical Science: Properties of objects and materials
Position and motion of objects
Light, heat, electricity, and magnetism
C: Life Science: The Characteristics of an Organism
D: Earth and Space Science: Objects in the sky
Changes in earth and sky
E: Science and Technology: Abilities of tech design
F: Science in Personal and Social Perspectives: Science and
technology in local challenges
G: History and Nature of Science: Science as a human endeavor
5-8
B: Physical Science: Motions and forces
Transfer of energy
C: Life Science: Structure and function in living systems
D: Earth and Space Science: Structure of the earth system
E: Science and Technology: Abilities of tech design
Understandings about science and technology
F: Science in Personal and Social Perspectives: Natural hazards
Risks and Benefits
Science and technology in society
G: History and Nature of Science: History of Science
9-12
B: Physical Science: Motions and forces
Conservation of energy
Interactions of energy and matter
D: Earth and Space Science: Energy in the earth system
Origin and evolution of the earth system
E: Science and Technology: Abilities of tech design
F: Science in Personal and Social Perspectives: Natural and
human-induced hazards
Paper Airplane Test Tunnel
National Science Content Standards
x
x
x
x
x
x
x
x
x
x
x
x
x
BIBLIOGRAPHY:
The American Heritage Dictionary of the English Language. 4th ed. Houghton Mifflin, 2000.
Apel, Willi, and Ralph T. Daniel. The Harvard Brief Dictionary of Music. NY: Pocket Books, 1961
Churchill, E. Richard. Amazing Science Experiments with Everyday Materials. Sterling, 1991.
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space Administration,
1998 (NASA EC-1998-03-002-ARC).
Eby, Denise and Robert B. Horton. Physical Science. NY: Macmillan, 1986.
Encarta Encyclopedia. CD-ROM. Microsoft Corporation. 2001.
Garrison, Tom. Oceanography: An Invitation to Marine Science. Belmont, CA: Wadsworth, Inc. 1993.
Hecht, Eugene. Optics. 2nd ed. Reading, MA: Addison-Wesley, 1987.
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., 1977.
Hewitt, Paul B. Conceptual Physics: A High School Physics Program. Addison Wesley, 1987.
Nave, Carl R. and Brenda C. Nave. Physics for the Health Sciences. Philadelphia: Saunders, 1980.
Notkin, Dr. Jerome J. et.al. The How and Why Wonder Book of Beginning Science. NY: Grosset & Dunlap,
1971.
Peterson, Roger Tory. A Field Guide to the Birds. 4th ed. Boston: Houghton Mifflin, 1980.
Serway, Raymond A. Physics for Scientists and Engineers with Modern Physics. 2nd ed. Saunders, 1986.
Take Flight. Museum of Science and Industry. Chicago. 2002.
WEB SITES
Please note: As of October 2002 when this manual was printed, all listed web sites were accessible via the
World Wide Web. Due to the unpredictable nature of the Internet, the existence of these sites cannot be
guaranteed after that time. In addition, while sites with reputable sources were carefully chosen, Carnegie
Science Center cannot be held responsible for the content or accuracy of the information posted on these
sites.
FLIGHT
The Bird Site.” The Natural History Museum of Los Angeles County Foundation.
http://www.nhm.org/birds/guide
FoilSim Download. http://www.lerc.nasa.gov/WWW/K-12/FoilSim/index.html
Legg, Gerald and David Salariya. The X-Ray Picture Book of Amazing Animals. NY: Franklin Watts,
1993.
United States Air Force Museum. Wright-Patterson AFB. OH.
http://www.wpafb.af.mil/museum/edu/soar2g.htm
108
FORCES OF NATURE
“Earthquake Hazards Program” United States Geological Survey. http://earthquake.usgs.gov/
“Exploring the Environment.” Wheeling Jesuit University/NASA Classroom of the Future™ . 1997-2002.
http://www.cotf.edu/ete/main.html
The Federal Emergency Management Agency. http://www.fema.gov/
Glasscoe, Maggi. “Earthquakes.” The Southern California Integrated GPS Network Education Module.
Updated 8/14/98. http://scign.jpl.nasa.gov/learn/eq.htm
Multidisciplinary Center for Earthquake Engineering Research. Information Service Research Foundation
of the State University of New York. http://mceer.buffalo.edu/infoService/
Natural Hazards Center at the University of Colorado, Boulder. http://www.colorado.edu/hazards/
“Natural Hazards Data.” National Geophysical Data Center.
http://www.ngdc.noaa.gov/seg/hazard/hazards.shtml
National Oceanic & Atmospheric Administration. http://www.noaa.gov/
National Severe Storms Laboratory. http://www.nssl.noaa.gov/
The National Park Service. http://www.nps.gov/
National Weather Service Tropical Prediction Center National Hurricane Center. http://www.nhc.noaa.gov/
Savage Earth. PBS Online. http://www.thirteen.org/savageearth/
Savage Seas. PBS Online. http://www.pbs.org/wnet/savageseas/
University of Illinois Online Guides: Meteorology. http://ww2010.atmos.uiuc.edu/(Gh)/guides/home.rxml
USA Today Weather Page. http://www.usatoday.com/weather/wfront.htm
United States Geological Survey. http://pubs.usgs.gov
The U.S. Global Change Research Information Office. http://www.gcrio.org/index.shtml
Volcano World. http://www.volcanoworld.org/
The Weather Channel. http://www.weather.com
The Weather Channel Storm Encyclopedia. http://www.weather.com/encyclopedia
Windows to the Universe. University Corporation for Atmospheric Research (UCAR). The Regents of the
University of Michigan. 2000. http://windows.arc.nasa.gov/
GENERAL EDUCATION / GENERAL SCIENCE
Annenberg / CPB Exhibits. http://www.learner.org/exhibits/
Discovery School.com. Lesson Plan Library 2002. http://school.discovery.com/lessonplans/
Exploratorium Snacks. The Exploratorium. CA. 2002. http://www.exploratorium.edu/snacks/
109
Hare, Jonathan D. The Creative Science Centre. School of Chemistry, Physics and Environmental Science,
University of Sussex, Falmer, Brighton. http://www.creative-science.org.uk/
The Learning Channel. The Learning Channel. Discovery Communications Inc. 2002.
http://tlc.discovery.com/
“The Thinking Fountain.” Science Learning Network. Science Museum of Minnesota. 1996.
http://www.sci.mus.mn.us/sln/tf/w/
ThinkQuest http://library.thinkquest.org
PHYSICS
Ellison, Patricia. Colorworm Teaches about Light and Color. 1997.
http://php.iupui.edu/~pellison/colorworm/home.html
Computer Animations of Physical Processes. Siltec Ltd. 2002.
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