Performance Benchmark P.12.C.1
Students know waves (i.e., sound, seismic, electromagnetic) have energy that can be
transferred when the waves interact with matter. E/S
Waves transmit energy that collapses buildings during an earthquake, carry energy in
which provides avenues for communication in today’s contemporary world, and produces
energy that allows for life on Earth to exist. Waves are basic features that occur in the
natural world and our ability to understand them has lead to the creation of some useful
devices such as satellites, cell phones, garage door openers, and microwave ovens.
Newton’s laws of motion and the conservation of energy principles govern the behaviors
of particles as well as the behaviors of waves. There are many kinds of waves; yet
regardless of type of wave, waves transfer energy when interacting with matter. All
energy can be considered either kinetic energy; the energy of motion; potential energy,
which depends on relative position; or energy contained by a field, such as
electromagnetic waves. Thus, in understanding the earth and how it carries its energy,
two general categories of waves are valuable: mechanical and electromagnetic waves.
Mechanical Waves
Mechanical waves are waves that require a medium (solid, liquid, or gas) to transmit its
energy from one location to another at a speed dependent upon the elasticity and inertial
properties of that medium. There are two basic types of mechanical waves: transverse
and longitudinal waves. These waves differ within their propagation regarding the wave’s
motion and the particle’s motion through which the waves are traveling in a medium.
Figure 1. The two types of mechanical waves: longitudinal and transverse
(from http://www.physicsclassroom.com/Class/waves/U10L1c.html)
In transverse mechanical waves, particles vibrate perpendicularly to the direction of the
wave energy propagation. The particles do not travel along the wave but simply oscillate
up and down about their individual equilibrium positions as the wave transports by. In
addition, transverse mechanical waves cannot pass through liquids or gases.
In longitudinal waves, particles vibrate parallel to the direction of the wave energy
propagation. The particles oscillate back and forth about their individual equilibrium
positions. There are parts where the air particles will be squished together, known as
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compressions, and other parts where they will be allowed to separate, known as
expansion or rarefaction.
To learn more about transverse and longitudinal mechanical waves, go to
http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html.
A great example of a longitudinal wave is a sound or acoustic wave. For example, wave
particles of air vibrate back and forth in the same and opposite direction of the energy
transfer as the sound wave travels from the lips of a speaker to the ear of a listener.
Individually, each particle pushes on its neighboring particle so as to push it forward.
This back and forth motion of the particles in the direction of the energy transfer creates
areas within the medium where the particles are compressed and expanded. This process
continues along the chain of particles until the sound wave reaches the ear of the listener.
Figure 2. Sound Wave (from
http://www.physicsclassroom.com/Class/waves/U10L1
c.html)
To learn more about sound waves, go to
http://www.physicsclassroom.com/Class/sound/soundtoc.html.
An example of transverse and longitudinal waves that occur simultaneously may be
found in seismic or earthquake waves. The longitudinal waves in earthquakes are called
P-waves or compression waves since they compress a material and pull apart in one
cycle. The transverse waves in earthquakes are called S-waves or shear waves since they
shear a material as they travel through it. P-waves shake the ground in the direction they
are propagating, while S-waves shake perpendicularly or transversely to the direction of
propagation.
To learn more about seismic waves, go to
http://www.skywise711.com/SeismicFAQ/SeismicFAQMain.html
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Figure 3. Seismic Waves (from
http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismicwaves.html)
Electromagnetic Waves
Unlike mechanical waves, which require a physical medium in order to transport their
energy, electromagnetic waves are capable of traveling through the vacuum of outer
space. Electromagnetic waves are created by accelerating vibrating charged particles,
such as electrons. These vibrating charges create a changing magnetic field, which in turn
create a changing electric field, which in turn creates a changing magnetic field, and the
process continues. The electric field and magnetic field lines are perpendicular to each
other, and both of these fields are perpendicular to the wave propagation. Therefore,
electromagnetic waves are transverse waves.
Figure 4. Oscillating Electric and Magnetic Waves
(from
http://www.monos.leidenuniv.nl/smo/index.html?basics/lig
ht.htm)
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Electromagnetic waves exist with a range of varying frequencies. The electromagnetic
spectrum is the continuous range of frequencies broken into specific regions; subdivided
into smaller spectra on the basis of how each region of electromagnetic waves interacts
with matter.
The electromagnetic spectrum includes from longest wavelength to shortest (or least
frequency to greatest): radio waves, microwaves, infrared, optical, ultraviolet, x-rays, and
gamma-rays. The wavelengths vary in size from very long radio waves about the size of
tall buildings, to short gamma-rays about the size of atom’s nucleus.
Figure 5. The electromagnetic spectrum (from
http://imagers.gsfc.nasa.gov/ems/waves3.html)
To learn more about electromagnetic waves, go to
http://imagers.gsfc.nasa.gov/ems/waves3.html.
In essence, sound waves, seismic waves, and electromagnetic waves carry energy that
can be transferred when the waves interact with matter.
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Performance Benchmark P.12.C.1
Students know waves (i.e., sound, seismic, electromagnetic) have energy that can be
transferred when the waves interact with matter. E/S
Common misconceptions associated with this benchmark:
1. Students incorrectly think that sounds can be produced without using any
material objects and that sounds can travel through empty space.
Sound waves are wave disturbances which are transported through a medium via particle
interaction; thus characterized as a mechanical wave in which requires a physical
medium; a series of interconnected and interacting particles that carry the wave. Sound
waves cannot travel through a vacuum of empty space. They require a physical medium
such as air. Without this physical medium, no sound would be heard. Sound waves
originate at the origin of a vibrating object, which creates the disturbance of the first
particle in the medium. This could be an example of a person’s vocal cords or vibrating
string and sound board of a guitar. The sound wave is transported from one location to
another by means of particle interaction moving through the entire medium as one
particle displaces another of its nearest neighbor from its equilibrium position.
More details about how the characteristics of sound are at
http://www.physicsclassroom.com/Class/sound/U11L1a.html
2. Students imagine sound waves as transverse waves rather than longitudinal
pressure waves.
Sound is a pressure wave. It involves particles of air that vibrate back and forth in the
same and opposite direction of the energy transfer. For example, a sound wave may travel
from the lips of a speaker to the ear of a listener, whilst each particle pushes on its
neighboring particle so as to push it forward. This back and forth motion of the particles
in the direction of the energy transfer creates areas within the medium where the particles
are compressed and expanded. This process continues along the chain of particles until
the sound wave reaches the ear of the listener. Since the particles of the medium are
moving in a direction parallel to the direction which the wave is moving, the sound wave
is referred to as a longitudinal pressure wave.
To learn more about how sound are longitudinal waves, go to
http://www.physicsclassroom.com/Class/sound/U11L1c.html
3. Students incorrectly think that when waves interact with a solid surface, the
waves are destroyed.
As a wave travels through a medium, it will often encounter the end of the medium and
begin another, known as a boundary. The behavior of the wave at that boundary is
referred to as boundary behavior. There are four possible boundary behaviors by which a
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wave could illustrate: reflection (the bouncing off of the boundary), diffraction (the
bending around the obstacle without crossing over the boundary), transmission (the
crossing of the boundary into the new material or obstacle), and refraction (occurs along
with transmission and is characterized by the subsequent change in speed and direction).
Energy being carried on a wave is not destroyed but simply transferred.
To learn more about boundary behavior, go to
http://www.physicsclassroom.com/Class/sound/U11L3c.html
4. Students incorrectly think that the spectrum of electromagnetic radiation consists
of only visible light.
The electromagnetic (EM) spectrum, commonly called light, is a group of similar waves
that vary by frequency (wavelength). EM waves are also called EM radiation (EMR),
where radiation is energy that travels and spreads out as it travels. EM waves (EMR)
consists of radio waves, microwaves, infrared and ultraviolet light, X-rays and gammarays; visible light frequencies are located between infrared and ultraviolet light.
Many students do not understand that radio is a form of light (EMR) and incorrectly
believe that radio waves are the same as sound waves. This misconception probably
stems from the fact that radio waves are used to transmit information that is later used to
produce sound in speakers and “radios” are the common name for these EM detectors
waves and converters.
To learn more about how we communicate with radio waves, go to
http://www.nrao.edu/whatisra/radio-anim.shtml.
Similar misconceptions occur with the other frequencies.
To find out more about X-rays as a form of light, go to
http://chandra.harvard.edu/xray_astro/xrays.html
To find out more out infrared light, go to
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/what_is_ir.html.
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Performance Benchmark P.12.C.1
Students know waves (I.e. sound, seismic, electromagnetic) have energy that can be
transferred when the waves interact with matter. E/S
Sample Test Questions
1. In order for a medium to be able to support a wave, the particles in the wave
must be
a. frictionless.
b. isolated from one another.
c. able to interact.
d. very light.
2. The diagram to the right represents a transverse
wave traveling in a string. The wave is transporting
energy from east to west. Which diagram best
represents the direction of vibration of the particles
in the string?
a.
c.
b.
d.
3. A wave is transporting energy from left to right. The particles of the medium
are moving back and forth in a leftward and rightward direction. Which type
of wave is this?
a. gravitational
b. electromagnetic
c. transverse
d. longitudinal
4. A sound wave is a mechanical wave; not an electromagnetic wave. This
means that
a. particles of the medium move perpendicular to the direction of energy
transport.
b. a sound wave transports its energy through a vacuum.
c. particles of the medium travel along the wave with the energy.
d. a medium is required in order for sound waves to transport energy.
5. Which of the following is NOT a characteristic of mechanical waves?
a. They consist of disturbances or oscillations of a medium.
b. They transport energy.
c. They travel through vacuums, as well as gases, liquids, and solids.
d. They are created by a vibrating source.
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6. The following figure represents a longitudinal wave. Which letter(s) represent
rarefactions?
a.
b.
c.
d.
A, B, and E
C only
B, D, and F
A, C, and E
7. The following figure represents a longitudinal wave. Which letter(s) represent
compressions?
a.
b.
c.
d.
A, C, and E
D only
A, C, and F
B, D, and F
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Performance Benchmark P.12.C.1
Students know waves (I.e. sound, seismic, electromagnetic) have energy that can be
transferred when the waves interact with matter. E/S
Answers to Sample Test Questions
1. (c)
2. (c)
3. (d)
4. (d)
5. (c)
6. (c)
7. (a)
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Performance Benchmark P.12.C.1
Students know waves (i.e. sound, seismic, electromagnetic) have energy that can be
transferred when the waves interact with matter. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Lessons on Waves: Light and Sound
The Physics Zone, a site maintained by Science Joy Wagon, provides an array
of excellent educational resources for students learning about waves;
specifically light and sound. Information is presented via Slide Show,
Simulation, Movie and Explanation, Interactive Lab (Java Applet),
Animations and Video (Quick Time), Lesson and Images, Pictures and
Descriptions, and Multiple Choice Practice. Though some links offered are for
members only, the following links are available and specific to this
benchmark:
 Reflection of a Pulse Wave
http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave6.html
 Periodic Wave Striking a New Medium
http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave5.html
2. Waves PhysicsQuest
Waves PhysicsQuest is a website created by Dolores Gende in which provides
learning about waves in the format of a webquest for students to complete on
the Internet. Students will learn about the nature and properties of waves.
They as well will see boundary behaviors of waves and how standing waves
are formed.
To access this site, go to http://physicsquest.homestead.com/quest7.html
3. Earthquakes – Things to Learn about – Exhibit Map (Simulations)
This site was created for the Hypertech online museum as a class project by
CMP 194, UCSC's course in advanced online publishing, taught by Marti
Atkinson. It is a production of EPIC, the Electronic Publishing Instructional
Curriculum. This site provides students with activities, background
information, and simulations regarding waves and earthquakes. Specifically,
the following links deal with mechanical waves and earthquakes:
 A Drop of Water
http://www.thetech.org/exhibits_events/online/quakes/waves/
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 The Slinky and The Rope
http://www.thetech.org/exhibits_events/online/quakes/waves/p&s_waves.
html
 A Shaking Record
http://www.thetech.org/exhibits_events/online/quakes/grams/
4. Electromagnetic Waves
This site provides students the opportunity to view electromagnetic waves
using Java Applets. Here students will be able to preview the latest
developments in interactive educational software for science and engineering
brought to you by Amanogawa.com.
To access the site, go to http://www.amanogawa.com/waves.html
5. Waves and Vibrations (Quia.com) – Flashcards
Students will be able to practice vocabulary terms for waves and vibrations.
You can view this flashcards at http://www.quia.com/fc/34849.html
6. Earthquakes/tectonics
This site developed by Scienceman.com; the ultimate educational resource,
which provides students with numerous links for studying Earthquakes and
waves. Specifically, the following links deal with Earthquakes:

Examine P and S waves moving through Earth's interior - control
this simulator and watch the waves move through Earth’s interior.
http://www.classzone.com/books/earth_science/terc/content/visualizations
/es1009/es1009page01.cfm?chapter_no=10
7. Build Your Own Seismograph
A site provided by howstuffworks.com, presents students with the opportunity
to create their own seismograph machine. Students will design a creative but
effective way to measure the seismic waves (shock waves) from an
earthquake. They will draw a clear diagram that shows and labels all parts.
Then write a paragraph explaining how their design works. A good design
would include the following:
a) made of common inexpensive materials found in a local store;
b) able to determine the relative magnitude (size) of each vibration it
measures;
c) able to measure vibrations continuously for at least one minute;
d) able to measure even slight vibrations (such as a person jumping up and
down next to your seismograph).
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Finally, they will gather their materials needed and build the seismograph they
designed. They will show other students how their device works.
To access the site go to,
http://science.howstuffworks.com/framed.htm?parent=question142.htm&url=
http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/Seismograph.html
8. Seismic Waves in Action
Coker College illustrates how Longitudinal (P) Seismic waves and Transverse
(S) Seismic waves travel individually and together in an earthquake via
simulation.
This site is located at
http://www.coker.edu/chemistry/courses/PHY101/Earth_and_Moon/seismic_f
lash.htm
9. Seismic Waves
For those that have access to an Internet lab, this series of lessons show
students the following concepts:
a) differentiate between 'P' and 'S' waves;
b) state which of the two types cannot travel through liquids;
c) describe how seismometers can detect 'P' and 'S' waves;
d) explain how data from seismometers all over the Earth's surface enable
scientists to model the path of waves through the Earth;
e) explain how earthquake "shadow zones" are formed;
f) describe how shadow zones provide information about the Earth's
structure; and
g) estimate sizes for the Earth's inner and outer core's.
These lessons were developed by Materials Teaching Educational Resources
© 1999 MATTER Project, The University of Liverpool and can be accessed at
http://www.matter.org.uk/schools/Content/Seismology/index.html.
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