Content Benchmark P.12.C.1
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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 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/U10L1c.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

Figure 3. Seismic Waves (from http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismic-waves.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/light.htm)

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)

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 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 gamma-rays; 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?

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.

6. The following figure represents a longitudinal wave. Which letter(s) represent rarefactions?

a. A, B, and E
b. C only
c. B, D, and F
d. A, C, and E

7. The following figure represents a longitudinal wave. Which letter(s) represent compressions?

a. A, C, and E
b. D only
c. A, C, and F
d. B, D, and F

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
Newton’s Challenge consists of three simple laboratory experiments, one for each law, which allows the students to obtain and comprehend a better understanding of the three laws of motion. Trimpe creates the experiment “pull the table cloth” trick for Newton’s First Law, hot wheelers carrying various masses down a ramp to represent Newton’s Second Law, and the use of straws and balloons to investigate Newton's Third Law by experimenting with several variations (angles), allowing the students to construct their own understanding of this law.

The challenges can be accessed at http://sciencespot.net/Pages/classphys.html#Anchor9
And the worksheets for these activities are at http://sciencespot.net/Media/newtonlab.pdf

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/

• 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).

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_flash.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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