Catch the Wave – 8.7 B
TAKS Objective 4 – The student will demonstrate an understanding of motion,
forces, and energy.
Learned Science Concepts

Unbalanced forces cause changes in the speed or direction of an
object’s motion.

Waves are generated and can travel through different media.
TEKS 8.7 Science concepts
The student knows that there is a relationship between force and motion. The
student is expected to:
(B) recognize that waves are generated and can travel through different
media.
Overview
To facilitate the discovery by the student that a relationship exists between force and
motion, to help him/her demonstrate the ability to recognize that waves are generated and
can travel through different media by
1. Discovering the existence of various kinds of waves;
2. Exploring the nature of longitudinal and transverse mechanical waves;
3. Characterizing waves with regard to period, frequency, amplitude and
velocity;
4. Measuring and developing skill in the measurement of wave speed;
5. Distinguishing between mechanical waves and Radio or Electromagnetic
waves;
6. Modeling seismic wave action.
Instructional Strategies
These objectives will be met using authentic methods of scientific inquiry; critical
thinking skills and scientific problem solving practices.
Objectives
1. The learner will be able to differentiate between the motion of the wave and the motion
of the matter carrying the wave.
2. The learner will identify waves that require a medium to move through and waves that
travel through empty space.
3. The learner will demonstrate that waves carry energy.
4. Students will generate waves that pass through different media.
5. The student will demonstrate that a wave moves forward while the material through
which it passes is displace only slightly and momentarily.
6. Students will measure wave properties.
For Teacher’s Eyes Only
Vocabulary
How Waves Move
Longitudinal- (aka Compression waves) – energy moves parallel to medium (Sound
waves, dominos, some earthquake)
Transverse- (aka S waves)- energy moves perpendicular (90º to medium
(electromagnetic waves -- radio, infrared, visible light, UV, Xrays . . .)
Two Major Types of Waves
Electromagnetic Waves - produced by the vibration of electrons within atoms on the
Sun's surface. Does not require particles to transfer energy; Usually transverse (S)
waves
Mechanical Waves - must have a medium to transfer energy. Need particles to interact
to transfer energy; Compression (sound), surface (water), both compression &
transverse (earthquakes)
Vacuum – a space with no matter- no air, no molecules, no atoms, nothing!
Waves are one of the most important forms of energy transmission that we know. Waves
come in many varieties: mechanical waves are actual motions of a material medium
while radio, light and X-rays are electromagnetic waves that are fluctuations in the
electromagnetic force that travel through empty space. There are other kinds of waves
too, such as the people “Wave” that we know from and enjoy at football games.
Incidentally, “The Wave” was created in 1981 by Mr. Bill Bissell, the long-time band
director of the University of Washington Husky Marching Band, although it is often
called the “Mexican Wave” since it was made popular at the 1986 World Cup Soccer
tournament in Mexico City. Scientists are also still searching for the faint oscillations in
the weak gravitational field of distant Black Holes that would signal the detection of
“Gravity Waves.” Even the toppling of dominoes that have been carefully lined up is a
wave of sorts.
When mechanical waves travel through a material medium, two possibilities exist for the
motion of the medium: along the direction of travel (called longitudinal) and
perpendicular to the direction of travel (called transverse). Only longitudinal waves can
travel through liquids and gases, but solids allow both. Seismic waves occur as both
varieties, longitudinal Pressure or P waves and transverse Shear or S waves. The P waves
travel significantly faster than do the S waves, a fact that permits the determination of the
distance to the epicenter of an earthquake. The waves you see on the surface of water
happens because the water near the surface moves in a circle, as anyone who has watched
a fishing cork waiting for a bite can affirm. A water-wave, then, is actually both a
transverse and a longitudinal wave because the water moves both up and down and back
and forth as a wave passes.
Mechanical waves have many properties in common. The height of the wave or the
distance the medium moves from its resting position is called the amplitude of the wave.
The time it takes for the wave to repeat the same up-and-down, back-and-forth or side-to-
side cycle is called the period of the wave; the period is measured in seconds. The
frequency of the wave is the same information as the period only expressed as how many
cycles happen in a second; the frequency is the inverse or reciprocal of the period and is
measured in the unit of Hertz (Hz). One Hertz is one cycle per second. In one period, the
wave will travel a certain distance so that the wave begins to repeat itself. This repeat
distance is called the wavelength. Because we have defined the frequency and
wavelength as we have, the speed of a wave is equal to its wavelength multiplied by the
frequency. In a formula
Speed of wave = wavelength x frequency
The speed of a mechanical wave is determined by only two properties of the material: (1)
the stiffness or springiness of the medium and (2) its inertia or the density. What
determines how fast a wave moves, then, is (1) how hard one piece of the medium pushes
or pulls on the other and (2) how much inertia that neighboring piece of material has. The
velocity of sound increases with temperature, since air—when it is heated—is less dense
than when it is colder, while on the other hand the springiness of the air is practically
unaffected by the higher temperature. So the lower density allows the disturbance to
travel faster from one part of the air to the next. At room temperature (20 C) the speed of
sound is about 343. meters per second (around 768 miles per hour). For every degree C
higher, the speed goes up by 0.6 m/s (1.3 mph). It goes down at the same rate as well.
Thinking along those same lines, because helium gas is very much less dense than air,
owing to the light mass of the helium atoms that make up the gas, and because the
springiness of helium is very nearly the same as air, helium has a much higher speed of
sound than does air. So, in general—all other things being equal—the less dense a
material is the faster is the speed of the wave.
But the speed of sound is much faster in water than it is in air even though water is about
eight hundred (800) times more massive than is air! Why is that? The difference is in the
stiffness of water relative to air. A bottle of air can easily be compressed; it makes a
“soft” spring. A bottle completely filled with water is very difficult to compress, on the
other hand. Water makes a very stiff spring if confined. Here the stiffness wins out over
the density to make the speed of sound about 1000 m/second, about three times the speed
of sound in air.
The concept of stiffness versus density is a very powerful concept for thinking about
mechanical waves. For example, it is easier to bend a piece of material than it is to crush
it. Thus rock is “stiffer” for longitudinal waves than it is for transverse waves. Transverse
seismic waves (S waves), that require the medium to bend, travel slower than
compression waves (P waves). This fact permits geophysicists to estimate the distance to
the epicenter of an earthquake by measuring the difference in the time of arrival of the P
and S waves. The time difference multiplied by the speed difference is equal to the
distance to the epicenter from the seismograph.
The difference in wave speed is important in other ways, too. Whenever there is an
abrupt change in the medium through which the wave is traveling, there is a reflection.
Seismic exploration takes advantage of this property of waves to reveal hidden geological
formations inside the earth’s crust that might have trapped petroleum or natural gas. As a
matter of fact, this is the only way that geophysicists and geologists have been able to
infer the internal structure of the earth with its crust, lithosphere and dense core. The
velocity of the seismic waves differs in each of the materials and echoes occur when ever
the sound wave crosses the boundary from one material to another.
The same approach has been used to get information about the interior of the sun: small
sun-quakes happen that are associated with solar flares. Then by a careful examination of
how the surface of the sun shakes, solar astrophysicists can figure out how the solar-wave
traveled inside the sun out of our sight. The same properties of reflection from materials
with different wave speeds even is used in ultrasound imaging to take a look at unborn
babies in very much the same way.
There is, however, another important class of waves that are very different in nature from
mechanical waves: the electromagnetic wave. EM waves, as they are sometimes called,
are “a disturbance in the force,” the electromagnetic force, that is. The EM force is the
force that makes your socks cling together when they come out of the drier; its what
makes plastic kitchen wrap cling to a bowl. Whenever lighting strikes, for example, a
huge discharge of electricity happens and the electric and magnetic fields in the space for
miles around are disturbed. The disturbance does not travel instantly out from the spark
but still it travels at a very high speed : 300 million meters per second or 186,000 miles
per second, about 1 million times faster than sound does. If you are listening to an AM
radio, the lightning strikes can be heard as static bursts of sound. EM waves happen
whenever a charge accelerates or an electrical current changes rapidly. Radio is an
example of just such an EM wave. But radio is not sound. Radio can travel through
empty space; sound, which requires a material medium, cannot. The information about
the sound is coded either as changes in the amplitude or frequency of the radio wave. The
radio receiver decodes the information and produces a sound that is like the one coded at
the radio studio. Television is also a radio wave in which not only the sound information,
but also the visual information (three colors and the brightness) is coded in a set of
companion radio waves.
Charges can be accelerated in other ways. When a material is heated the atoms begin to
move to and fro. This causes the charges of the nuclei to be accelerated. EM waves are
produced—radiant heat, infrared radiation. If the material is hotter it becomes
incandescent, it glows. The atoms are moving fast enough to produce EM waves whose
frequency is the range of visible light. Even hotter and one detects ultraviolet light.
If one takes an electron, accelerates it with a high voltage and allows it to run into a
molybdenum slug, it will be stopped very suddenly. This abrupt deceleration will cause a
burst of EM radiation of very high frequency and short wavelength. Originally these rays
were not identified and were called X-rays, for the unknown ray. Later scientists learned
that X-rays are just penetrating cousins of more familiar EM waves in the
electromagnetic spectrum. That’s what that device is doing in the dentist’s office when
you get dental X-rays; it is making electromagnetic waves by slamming electrons into a
target to get X-rays when they stop suddenly.
All waves carry energy from one place to another. In the case of EM waves we feel the
heat energy from a campfire; microwaves heat our muffins; sunlight warms us on a
winter morning. The electric fields of EM waves make the electrons in materials move.
The electrons bump into the atoms, making them move. When the atoms move, heat
happens, and the energy is absorbed by the object. No electricity flows from the radiator,
only energy in the form of a disturbance in the electric and magnetic field. The source of
the energy may be trillions of miles away, as is the case with distant galaxies whose light
we see after billions of years of travel.
Mechanical waves carry energy, too, even if the medium does not flow from the source;
rather, one part of the medium “hand off” the energy to the next and then to the next and
so on until it reaches you. Our ears are incredibly sensitive. The average human can
detect a sound whose sound energy intensity is equivalent to the light intensity of a 100
Watt reading lamp being viewed at a distance of about 2000 miles! Clearly earthquakes
carry an immense amount of energy in the seismic waves. The Richter scale is a measure
of the amount of energy released by the earthquake at its source. A helpful (but somewhat
advanced) source of information is the University of Nevada, Reno, Seismological
Laboratory, http://www.seismo.unr.edu
Even dominoes falling down, one after the other, send energy down the chain. And let’s
not forget the nimble surfers who slide down the face of rapidly advancing ocean waves.
The energy that propels them forward is the energy of the water wave that lifts them up.
Instead of being lifted first up, then down at the wave passes, the surfboard allows them
to stay continually on the lifting side of the wave and to exploit the energy of the wave,
and that’s not to speak of the exhilarating ride that they enjoy.
Waves are everywhere and share many interesting features. We hope this little tutorial
will help you enjoy Catching the Wave!
Summary:

There are many kinds of waves.

Mechanical waves can be transverse or longitudinal.

Mechanical waves are a form of motion in which one part of the object
moves relative to another, rather than an overall motion of the object from
one place to another.

Amplitude is the size of a wave.

Period is the time it takes to make one oscillation

Frequency is how many times in a second a wave wiggles.

Wavelength is the distance from one point a wave to a corresponding point
on the next cycle.

Radio, light, heat radiation, microwaves and X-rays are all
electromagnetic waves that do not require any medium other than space.

All mechanical waves need a material medium to shake.

The speed of a mechanical wave is determined by how stiff and how dense
is the medium.

Seismic waves are of two types: longitudinal P-waves and transverse Swaves.

Waves carry energy from one place to another without the medium
moving nearly as far.
Student Misconceptions
 Misconception
When waves—particularly sound waves—move, the media flows from the source
to the observer, like a river.
 Science Concept
In fact, the medium moves very little. In the case of sound waves the motion of
the air is only about the thickness of a human hair.
Rebuild Concept
Use physical examples in the cheerleader wave or the domino fall to show the
wave moves but the medium does not.
 Misconception
Radio waves are sound waves
 Science Concept
The radio is not sound. Radio waves are “a disturbance in the force,” the
electromagnetic force, that is. The information about the sound is coded either in
the strength (amplitude) of the disturbance to produce Amplitude Modulated
(AM) radio or in the frequency to make Frequency Modulated (FM) radio. ( XM
radio is just FM radio broadcast from satellites.)
Rebuild Concept
Point out that radio waves move through space where there is no medium.
 Misconception
There is sound in the vacuum of space.
 Science Concept
Sound is a mechanical wave that requires a material medium to shake. There is no
air in Outer Space; therefore sound cannot travel through the emptiness of space.
Rebuild Concept
Use a bell jar vacuum system and ringing bell. As the bell jar is evacuated the
ringing gets dimmer until it can no longer be heard.
 Misconception
Sound moves up and down and left to right, that is, it is a transverse wave.
 Science Concept
The molecules of air move forward and backward along the direction the wave is
traveling, a longitudinal wave. Fluids like air and water have no way to allow a
transverse wave to travel through them.
Rebuild Concept
Use a slinky to demonstrate longitudinal and transverse waves. Show a simulation
of compression waves hitting the ear drum to show how sound is transmitted to
the ear.
Student Prior Knowledge
Waves are not introduced in the sixth and seventh grade TEKS. In order to build upon
learning experiences, students must understand the motion of matter, understand the
concert of energy, and know what is meant by a medium.
5 E’s
Engage
Engage One
Darken the room and use a flashlight shining on your face to emulate the telling of a
ghost story. Play thunderstorm sound effects. Narrate the following story:
“It was a dark and stormy night. John was listening to the weather report on the radio. A
severe thunderstorm was approaching rapidly. As he listened to the meteorologists he
heard a faint sound every now and then that sounded like “sfzt! sfzt!” then several
minutes later he hear a distant rumble of thunder. As the minutes passed, the time
between the static-like sound on the radio and the sound of the thunder grew smaller and
smaller. At last, John realized that the sound on the radio occurred at the same time he
saw the flash of lightning. He counted, “1001,1002, 1003, 1004, 1005” “Boom!” “That
was a mile away,” he remarked. What was John hearing on the radio? (Answer: the
electrical “static” or “electrical noise” from the lightning discharge, actually an
electromagnetic wave that flew out from the burst of electricity in the lightning bolt).
How did John figure out what the sound was on the radio?
What was John doing, counting 1001, 1002 etc (Answer: counting seconds. Sound travels
about 1 mile in five seconds. Radio waves travel a million times faster.)
Engage Two
Demonstration: Poof
Materials:
Balloon
Paper monsters (Black Line Masters)
Half Gallon Milk Jug
Tape
Procedure: Create a compression (longitudinal) wave to knock down a paper monster.
Print the paper monsters from the Black Line Masters and fold in half long way so they
stand. Cut the bottom from a half gallon milk jug. Stretch a balloon across the bottom and
tape securely. Point the mouth of the jug toward the monster several feet away. Hit the
balloon bottom with a firm thud and knock over the monster. The balloon diaphragm sets
up a single compression wave impulse, which travels several feet through the air.
Smoke can be added to the milk jug and smoke rings created. Incense, chalk dust or dry
ice can be a source of the smoke.
Engage Three
Activity: “Cheerleader” wave
Class Time: 10 minutes
Objective: The learner will be able to differentiate between the motion of the wave and
the motion of the matter carrying the wave.
Procedure: The student will demonstrate that a wave moves forward while the material
through which it passes is displace only slightly and momentarily.
Have students form a circle. Point to one student to start “The Wave” that they are
familiar with from football games. After they have done it a few times (l or 3) ask, “Are
you the wave?”
Lead students to realize that the wave is more than each of them. The wave is the motion
of the object. They are the “medium.”
Follow up by noting that they are moving up and down while the wave is moving down
the line. They are moving “transverse” meaning “across.” This is a transverse wave.
Then have the students turn and put their hands on the shoulders of the person in front of
them to form a “Conga Line.” Have them do to the person in front of them what was
done to them. Give the first person a gentle push on the shoulders. A rippling wave will
travel down the line. Have them reverse directions and repeat. Discuss how this is now
also a wave. But this time the motion is “along the direction of the wave’s direction of
travel.” This is called a “longitudinal” wave.
Explore
Exploration 1
Activity: Falling like dominoes
Class Time: 20 minutes
Objective: The learner will demonstrate that waves carry energy.
Materials:
50 or more dominoes per group
Procedure: Give each group of students between 50 and 100 dominoes. Let the group
build what ever formation they choose by lining up the dominoes. The energy added to
the first domino should cause something to happen.
Explain
Wave: a collective or cooperative motion of a medium.
Mechanical wave: a wave that is an actual motion of the object.
Wave Motion: wave motion is a moving of one part of an object relative to another part.
Wave generation: a movement of a part of an object in a cycle that repeats.
Medium: the “stuff” that the wave travels through.
In 1896 Guglielmo Marconi applied for the patent on the first commercial “wireless
telegraph,” the radio. He used a greatly improved device over the one first used by
Heinrich Hertz. Marconi sent “Hertzian waves” through the air that caused a spark to
jump between electrodes. Communication was via the Morse code commonly used in
land-line telegraphs. In 1900 Marconi founded the Wireless Telegraph Company. In
April 1912, the Titanic struck an iceberg and sank. Many people died but “those who
survived owed their lives to the distress calls from the Marconi wireless equipment on
board. As the Right Hon. Herbert Samuel, Postmaster General at the time, stated: ‘Those
who had been saved, had been saved through one man, Mr. Marconi and…his marvelous
invention.’” http://www.marconi.com/html/about/marconihistory.htm (April 8, 2004.)
Examples
Sound waves, string waves, seismic waves, water waves, surf, waves of automobile
traffic on the freeway, domino waves, radio waves, light waves, “gossip waves,” slinky
waves, “The Mexican Wave” at football games (called the Mexican wave because it
appeared at the ‘86 World Cup Soccer tournament in Mexico.)
 Sound waves are everywhere. Put your hand on your throat and speak.
Do you feel the vibrations? Inside your larynx or voice box folds of
mucus membrane called vocal folds chop the air to make sound. The
air vibrates inside your throat making sound waves that travel to your
ear.

Radio waves and light are electromagnetic waves that are oscillations
of electric fields. When someone uses an electrical appliance or tool
that has an electric motor, sometimes we hear static on the AM radio
because of the electrical sparks generated in the motor.

Lightning is a large electrical spark that heats the air and at the same
time makes a large electrical oscillation. Two kinds of waves are
produced: sound from the explosive heating of the air and an
electromagnetic wave in the form of light and radio interference.
Sound waves travel at about 1/5 mile in a second while light waves
travel a million times faster. So you see the flash almost at the same
time it happens, while the sound of the thunder gets there five seconds
later for every mile the lightning bolt is from you. The thunder
sometimes rumbles because the lightning bolt is spread out over a long
pathway and the sound from the near end gets to your ear before the
sound from the far end.
Class discussion question process:
What are some examples of waves? Example answer – Ocean waves
Through what medium does the wave travel? Example answer – water
How does the wave demonstrate that it carries energy? Example answer – it washes sand
up onto the beach or it erodes the beach.
Group discussion:
In groups of 3-5 allow students to discuss what the world would be like without waves.
After the discussion the group should report their conclusions to the class.
Elaborate
Elaboration One
Activity: I Can Hear You
Class Time: 20 minutes
Objective: Students will generate waves that pass through different media.
Materials:
(Per Group)
2 Styrofoam cups, paper cups, or “tin” cans
20-50 feet of string
2 paper clips
Activity:
7. Poke a hole through the bottom of each cup. Feed
the string through the hole and tie it to a paper clip
inside the cup. This secures the string. (See
Diagram)
8. Stretch the string tight. Take turns talking into the
cup.
9. Describe how the waves are transmitted. Voice
vibrates the air, which in turn vibrates the cup.
The cup vibrates the string. The waves travel
down the string and vibrate the opposite cup,
which causes the air to vibrate thus vibrating the
eardrum causing us to hear the sound originating from the initial cup.
1. Experiment with different string or different types of “cups”.
2. Describe how different materials react.
Elaboration Two
Activity: Making Waves
Class Time: 45 minutes (Less if apparatus is pre-made)
Objective: The student will demonstrate that a wave moves forward while the material
through which it passes is displace only slightly and momentarily.
Materials:
Soda Straws (50 or per group)
scotch tape
Hot glue and glue gun
2 large nails for each soda straw
Ruler
Stop watch
Procedure:
1. Build the wave machine: Lay 2 meters of tape on table, sticky side up. Arrange
straws perpendicular to tape- TAPE SHOULD RUN DOWN CENTER OF
STRAWS!!! Straws should be ~ 2cm apart. Lay another length of tape over the
straws/tape making a tape-straw-tape sandwich. Tape should be centered.
*** Optional ***
2. To add more weight to the straws, hot glue nails or small washers to the open
Soda Straw
Tape
Nail
ends of each straw.
3. Hold the tape at the top and bottom. Rotate the top or the bottom soda straw and
release it.
4. Time how long it takes a transverse wave to travel the length of the string. Does it
matter if you start the wave at the top of the string or the bottom of the string?
5. Create a compression wave by tapping one straw near the bottom (works best if
two people hold the wave machine taught). Time the compression wave as it
travels the length of the string. Is the time different from the first generated wave?
6. Test wave machines with different spacing of straws. Does the spacing of the
straws make a difference in the time it takes for the wave to travel?
Elaboration Three
Activity: You Light Up My Life
Class Time: 20 minutes
Objective: Students will generate waves that pass through different media.
Materials:
Metal can with both ends removed
Balloon
Tape
Small Mirror
Glue
Laser (small diode Laser works well)
Procedure:
1. Cut the balloon and stretch it over one end of the can. Tape securely. Glue a small
piece of mirror to the balloon bottom. Glue it about halfway from the center to the
edge of the bottom.
2. Mount the can at a comfortable height for talking into. Make sure the balloon end
of the can is pointing toward a wall.
3. Mount the Laser so that the light bounces off the mirror on the can and hits the
wall. Caution – do not let the Laser beam shine into
anyone’s eye!
4. Talk, sing, yell or scream into the can. Figures will dance on the wall.
Elaboration Four
Activity: Wave Generator
Class Time: 20 minutes
Objective: The student will count, and measure wavelengths of transverse (S) waves.
Materials:
single double A battery clip
1.5-3.0 DC motor (hobby motor)
double A battery
5 cm. 1/4 “dowel rod with a predrilled 1/16” hole located approximately 1.5 cm
from one end of the dowel rod
20 cm electrician tape
1 meter of cord
Procedure:
1. Tie a knot in one end of the cord. Insert the unknotted end of the cord through the
hole opposite the spring in the battery clip. Pull the string through the hole so that
the knot is tight against the wall of the batter clip.
2. Properly insert the battery.
3. Use electrician tape to attach the CD motor to the spring end of the battery clip.
The top of the battery clip and the CD motor should be level.
4. Place the pin of the CD motor into the predrilled dowel rod.
5. CAUTION!! When completing this step the circuit is complete and the motor
will cause the dowel rod to spin rapidly which could hazardous to you hands.
Hook the exposed ends of the battery clip wires to the electrodes on bottom of the
DC motor. Hook the red wire to one side and the black wire to the other side to
complete the circuit.
Evaluate
Assessment tools:
Assess student understanding of the types of wave motion by having the student
write a brief paragraph detailing three different kinds of waves and the medium
through which they move. Students may also illustrate their descriptions.
Create an illustrated poem (cinquain, haiku, limerick) for each type of wave.
KNOCK-DOWN MONSTERS
Falling Like Dominoes
Class Time: 20 minutes
Objective: The learner will demonstrate that waves carry energy.
Materials:
50 or more dominoes per group
Procedure:
1. Line up your dominos to build a formation.
2. When you are ready, gently knock down the first domino. Observe what happens
to the rest!
3. Did energy move from the first domino to the last? How do you know?
4. Did the dominos change position from the first to the last or stay in the same
place?
5. What is transferred through wave- energy? matter? both? neither? Give
evidence from the lab to prove your point.
I Can Hear You
Class Time: 20 minutes
Objective: Students will generate waves that pass through different media.
Materials:
(Per Group)
2 Styrofoam cups, paper cups, or “tin” cans
3 – 10 meters of string per group
2 paper clips
Activity:
1. Poke a hole through the bottom of each
cup. Feed the string through the hole and
tie it to a paper clip inside the cup. This
secures the string. (See Diagram)
2. Stretch the string tight. Take turns talking
into the cup.
3. Describe how the waves are transmitted.
Voice vibrates the air, which in turn
vibrates the cup. The cup vibrates the
string. The waves travel down the string
and vibrate the opposite cup, which causes
the air to vibrate thus vibrating the
eardrum causing us to hear the sound
originating from the initial cup.
4. Experiment with different string or different types of “cups”.
5. Describe how different materials react.
Making Waves
Class Time: 45 minutes (Less if apparatus is pre-made)
Objective: The student will demonstrate that a wave moves forward while the material
through which it passes is displace only slightly and momentarily.
Materials:
Soda Straws (50 or per group)
Scotch tape
Hot glue and glue gun
2 large nails for each soda straw
Ruler
Stop watch
Procedure:
1. Build the wave machine: Lay 2 meters of tape on table, sticky side up. Arrange
straws perpendicular to tape- TAPE SHOULD RUN DOWN CENTER OF
STRAWS!!! Straws should be ~ 2cm apart. Lay another length of tape (stickyside down) over the straws/tape making a tape-straw-tape sandwich. Tape should
be centered.
Soda Straw
Tape
Nail
2. **** Optional ****To add more weight to the straws, hot glue nails or small
washers to the open ends of each straw.
3. Hold the tape at the top and bottom. Rotate the top or the bottom soda straw and
release it.
4. Time how long it takes a transverse wave to travel the length of the tape. Does it
matter if you start the wave at the top of the string or the bottom of the tape?
5. Create a compression wave by tapping one straw near the bottom (works best if
two people hold the wave machine taught). Time the compression wave as it
travels the length of the tape. Does it matter if you start at the top or bottom?
6. Is one type of wave faster than the other? Which one?
7. Test wave machines with different spacing of straws. Does the spacing of the
straws make a difference in the time it takes for the wave to travel?
TRANSVERSE WAVE
time (sec)
start at bottom
start at top
COMPRESSION WAVE
time (s
start at bottom
start at top
You Light up My Life
Class Time: 20 minutes
Objective: Students will generate waves that pass through different media.
Materials:
Metal can with both ends removed
Balloon
Tape
Small Mirror
Glue
Laser (small diode Laser works well)
Procedure:
1. Cut the balloon and stretch it over one end of the can. Tape securely. Glue a small piece
of mirror to the balloon bottom. Glue it about halfway from the center to the edge of the
bottom.
2. Mount the can at a comfortable height for talking into. Make sure the balloon end of the
can is pointing toward a wall.
3. Mount the Laser so that the light bounces off the mirror on the can and hits the wall.
Caution – do not let the Laser beam shine into anyone’s eye!
4. Talk, sing, yell or scream into the can. Figures will dance on the wall.
5. Do low notes or high notes make better shapes?
6. Try all your vowels (a, e, i, o, u). Which vowel makes the best shapes?
Wall
Wave Generator
Class Time: 20 minutes
Objectives: .The student will count, and measure wavelengths of transverse (S) waves.
Materials:
single double A battery clip
1.5-3.0 DC motor (hobby motor)
double A battery
5 cm. 1/4 “dowel rod with a predrilled 1/16” hole located approximately 1.5 cm
from one end of the dowel rod
20 cm electrician tape
1 meter of cord
Procedure:
6. Tie a knot in one end of the cord. Insert the unknotted end of the cord through the
hole opposite the spring in the battery clip. Pull the string through the hole so that
the knot is tight against the wall of the batter clip.
7. Properly insert the battery.
8. Use electrician tape to attach the CD motor to the spring end of the battery clip.
The top of the battery clip and the CD motor should be level.
9. Place the pin of the CD motor into the predrilled dowel rod.
10. CAUTION!! When completing this step the circuit is complete and the motor
will cause the dowel rod to spin rapidly which could hazardous to you hands.
Hook the exposed ends of the battery clip wires to the electrodes on bottom of the
DC motor. Hook the red wire to one side and the black wire to the other side to
complete the circuit.