TheNature of Waves - InfobaseFor instance, in space there is little or no medium. 41. And yet, light from the sun and stars travels through the vacuum of space all the way to Earth

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Teacher's Guide

TheNatureofWaves

Editors:Brian A. Jerome, Ph.D.Stephanie Zak Jerome

Assistant Editors:Anneliese BrownLouise Marrier

Graphics:Lyndsey Canfield

Dean LadagoFred Thodal

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Table of Contents2

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A Message from our Company

Viewing Clearances

Use and Copyright

National Standards Correlations

Student Learning Objectives

Assessment

Introducing the Program

Program Viewing Suggestions

Video Script

Answer Key to Student Assessments

Answer Key to Student Activities

Pre-Test

Post-Test

Video Review

Vocabulary

Writing Activity

Waves and Mediums

Wave Characteristics

Experimenting with Refl ection


National Standards CorrelationsBenchmarks for Science Literacy(Project 2061 - AAAS)

National Science Education Standards(Content Standards: K-4, National Academy of Sciences)

Grades 3-5

As a result of their activities in grades 5-8, all students should develop an understanding of:

The Physical Setting - Motion (4F)By the end of 8th grade, students should know that:• Vibrations in materials set up wavelike disturbances that spread away from the source. Sound and earthquake waves are examples. These and other waves move at different speeds in different materials.

Physical Science - Content Standard B

Interactions of Energy and Matter

• Waves, including sound and seismic waves, waves on water, and light waves, have energy and can transfer energy when they interact with matter.

By the end of 12th grade, students should know that:

• Waves can superpose on one another, bend around corners, refl ect off surfaces, be absorbed by materials they enter, and change direction when entering a new material. All these effects vary with wavelength. The energy of waves (like any form of energy) can be changed into other forms of energy.

• Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways.

• Light interacts with matter by transmission (including refraction), absorption, or scattering (including refl ection). To see an object, light from that object - emitted by or scattered from it - must enter the eye.

Transfer of Energy

As a result of their activities in grades 9-12, all students should develop an understanding of:


Student Learning ObjectivesUpon viewing the video and completing the enclosed student activities, students will be able to do the following:

• Defi ne waves as traveling disturbances that carry energy through matter or space.

• Explain that waves do not actually move matter. Instead, waves fl ow through matter or create a disturbance in it.

• Understand that energy, often in the form of vibrations, is necessary to produce waves.

• Defi ne a medium as a substance, or matter through which a wave travels.

• Provide examples of waves traveling through the following mediums: solids, liquids, and gases (air).

• Sketch a simple diagram of a transverse wave.

• Describe how the particles in a transverse wave move across or perpendicular to the direction the wave is traveling.

• Explain how the particles in a longitudinal wave vibrate back and forth, parallel to the direction the wave is moving.

• Cite examples of transverse and longitudinal waves.

• Understand that waves have several different characteristics. Briefl y defi ne the following wave characteristics: - amplitude - wavelength - frequency

• Explain that refl ection occurs when a wave bounces back after striking something.

• Understand that an echo involves the refl ection of sound waves, whereas a mirror refl ects light waves.

• Describe refraction as the process of light changing direction, or bending, when it passes from one medium to another.


The Post-Test can be utilized as an assessment tool following student completion of the program and student activities. The results of the Post-Test can be compared against the results of the Preliminary Test to assess student progress.

The Preliminary Test is an assessment tool designed to gain an understanding of students’ preexisting knowledge. It can also be used as a benchmark upon which to assess student progress based on the objectives stated on the previous pages.

Assessment

Preliminary Test (p. 14-15):

Video Review (p. 18):

Post-Test (p. 16-17):

The Video Review can be used as an assessment tool or as a student activity. There are two sections. The fi rst part contains questions displayed during the program. The second part consists of a fi ve-question video quiz to be answered at the end of the video.


Introducing the Program

Program Viewing SuggestionsThe student master “Video Review” (p. 18) is provided for distribution to students. You may choose to have your students complete this master while viewing the program or do so upon its conclusion.

The program is approximately 14 minutes in length and includes a fi ve-question video quiz. Answers are not provided to the Video Quiz in the video, but are included in this guide on page 12. You may choose to grade student quizzes as an assessment tool or to review the answers in class.

The video is content-rich with numerous vocabulary words. For this reason you may want to periodically stop the video to review and discuss new terminology and concepts.

Before showing the video program to the students ask them what enables them to see objects around the room. Next, ask them what enables them to hear your voice. Tell them that light reaching their eyes, and sound reaching their ears are in the form of waves. Explain that these are just a couple examples of waves we commonly experience.

Write the term “wave” on the board. Ask students what the term means to them. Many will say the term means waves on the ocean or lake. Explain that a wave is a traveling disturbance that carries energy through matter or space. Tell students to pay close attention to the program to learn more about the characteristics of waves.


Video Script 1. If you have ever been to an ocean beach, you have probably enjoyed playing in the

waves. 2. Maybe you’ve had the thrill of surfi ng on ocean waves. 3. If you have done either of these things, then you are probably quite familiar with

waves. 4. But, did you know there are many other types of waves – many of which we cannot

see. 5. For example, radio waves traveling invisibly through the air can be picked up by

radios. 6. And sound waves enable us to hear music. 7. So, what exactly are waves? 8. What are some of the characteristics of waves? 9. And what are the different types of waves?10. During the next few minutes we are going to explore these questions and others...11. ...as we investigate the nature of waves.12. Graphic Transition – What are Waves?13. If you have ever used a microwave oven,...14. ...sailed on the ocean,...15. ...or been in an earthquake, you have experienced waves.16. What exactly is a wave?17. A wave is a traveling disturbance that carries energy through matter or space.18. A wave does not actually move matter. Instead, it fl ows through matter or creates a

disturbance in it.19. For example, sound waves travel through the air, but the air does not travel with the

wave. 20. If air did travel with sound waves, you would feel a rush of air every time the phone

rang!21. Waves transfer energy from one place to another.22. Energy, often in the form of vibrations, is necessary to produce waves. A vibration

is a movement that repeatedly follows the same path. A wave is the outward movement of energy from a vibrating source.

23. You Observe! What do you notice when this guitar string is plucked?24. You can see the string vibrating back and forth.25. The vibrating string creates sound waves that travel through the air. We hear these

sound waves as music.26. Here is another example. As the propeller on this boat motor rapidly spins, it

transfers energy to the water.27. The propeller, along with the boat, create a wave that travels through the water.28. Let’s now take a look at the materials through which waves travel.29. Graphic Transition – Mediums and Waves30. You have probably heard or even felt sound waves that travel through the air.31. But did you know that sound waves can also travel through solids?


Video Script32. Place your ear on a table and have someone scratch the far end of the table. You

can hear the scratching sound because it traveled through the solid table.33. Sound waves can also travel through water. Animals, like dolphins and whales, can

detect sound waves hundreds of kilometers away.34. These examples illustrate how sound waves travel through different mediums.35. A medium is the substance, or matter, through which a wave travels.36. Liquids, solids, and gases are all mediums.37. Mechanical waves, such as sound waves and seismic waves – those are the waves

responsible for causing earthquakes – need a medium through which to travel.38. But, not all waves need to travel through a medium.39. Electromagnetic waves, such as light, do not need a medium through which to travel.40. For instance, in space there is little or no medium.41. And yet, light from the sun and stars travels through the vacuum of space all the way

to Earth.42. Graphic Transition – Types of Waves43. Let’s take a look at a couple of different types of waves. 44. You Decide! Describe how the waves in this rope move.45. The waves move up and down. You might say the waves in the rope move at right

angles, or perpendicularly to, the motion of the wave.46. The wave in the rope is a type of wave called a transverse wave.47. In a transverse wave the particles move across, or perpendicular to the direction the

wave is traveling.48. Light and other electromagnetic waves, including radio waves and microwaves, are

transverse waves.49. A longitudinal wave is another type of wave. In a longitudinal wave, particles of the

medium vibrate back and forth, parallel to the direction the wave is moving.50. This can be demonstrated with a spring-like slinky toy. 51. When the end of the spring is pushed back and forth, notice how parts of the spring

are compressed and other parts are more spread apart.52. The energy traveling through the spring creates a wave.53. Sound waves are examples of longitudinal waves.54. When a sound wave moves from left to right, air particles collide with other nearby

air particles and form an area of compression.55. Then the fi rst set of air particles moves to the left while the second set of particles

vibrates and moves to the right. This leaves a space containing many fewer particles, called a rarefaction. As the particles compress and separate, the wave moves forward.

56. Some sound waves, such as those generated by airplanes...57. ...and fi reworks, can produce very powerful longitudinal waves.58. Graphic Transition – Properties of Waves59. Waves have several different characteristics or properties, including amplitude,

wavelength, and frequency.


Video Script60. In this diagram of a transverse wave, the high points are called crests and the

low points are called troughs. Halfway between the crest and trough is the resting position.

61. The amplitude of a wave is a property that indicates how much energy a wave has.62. Amplitude is determined by measuring the distance between a wave’s resting point

and its trough, or between its resting point and its crest.63. You Compare! Which wave has a greater amplitude, wave A or wave B?64. Wave B has a greater amplitude.65. Waves with high amplitude, such as these huge ocean waves, have more energy...66. ...than these smaller waves.67. Wavelength is another property of waves. A wavelength is the distance between any

two adjacent crests, or between any two adjacent troughs.68. Frequency is another property. Wave frequency is the number of complete waves

that pass a given point in a certain period of time. 69. When we slowly move the rope, the number of waves passing this point is low. We

can say the rope has a low frequency.70. But when we move the rope more quickly, the frequency increases.71. Graphic Transition – Interaction of Waves72. Whenever you look in the mirror...73. ...or admire the moon, you are witnessing one of the ways light interacts with matter

– refl ection.74. Refl ection occurs when a wave bounces back after striking something.75. You Observe! What do you hear after this person shouts?76. You hear her voice again and again.77. This is called an echo. An echo involves the refl ection of sound waves.78. Waves usually travel in straight lines, but when they pass from one medium into

another, they slow down and immediately change direction.79. Refraction is the bending of a wave as it passes at an angle from one medium to

another medium.80. For example, when light waves travel from the air into water, they slow down and

immediately change direction.81. Refraction is responsible for causing the pencil in this glass of water to appear as if it

is bent.82. These are just a few of the many examples of wave interaction.83. Graphic Transition – Summing Up84. During the past few minutes we have explored some of the fascinating

characteristics of waves.85. We began by learning that a wave is a disturbance that carries energy as it moves

through matter or space.86. Waves can travel through many different mediums, including solids, liquids, and

gases.


Video Script87. We also learned that electromagnetic waves can travel without a medium, for

instance, through space.88. We discussed different types of waves, such as transverse waves and longitudinal

waves.89. The properties of waves were highlighted, including amplitude, wavelength, and

frequency.90. Finally, we investigated the various interactions of waves, including refraction and

refl ection.91. So, the next time you swim in the ocean,...92. ...hear the echo of a far away noise,...93. ...think about some of the things we just discussed. You might just think about

waves a little differently.94. Graphic Transition – Video AssessmentFill in the correct word to complete the sentence. Good luck and let’s get started. 1. ________ transfer energy from place to place. 2. A _________ is a movement that repeatedly follows the same path.

3. A ________ is the substance, or matter, through which a wave travels. 4. Sound waves are examples of _________ waves. 5. _____ occurs when a wave bounces back after striking something.


Answer Key to Student AssessmentsPre-Test (p. 14-15) Post-Test (p. 16-17)

Video Review (p. 18)

1. You can see the guitar string vibrating back and forth.2. The waves in the rope move up and down.3. Wave B has a greater amplitude.4. You hear her voice again and again. This is called an echo

1. Waves transfer energy from place to place.2. A vibration is a movement that repeatedly follows the same path.3. A medium is the substance, or matter, through which a wave travels.4. Sound waves are examples of longitudinal waves.5. Refl ection occurs when a wave bounces back after striking something.

1. b - energy 2. d - vibrations 3. c - air 4. a - medium 5. a - transverse waves 6. d - crest 7. d - bounces back 8. a - echo 9. d - change direction10. b - refraction 11. true12. false13. false14. true15. false16. A wave is a traveling disturbance that carries energy through matter or space.17. Most waves are produced by vibrations in moving objects or other matter. 18. Sound can travel through solids, liquids, and gases.19. Examples of transverse waves include light, radio waves, and microwaves.20. Refl ection occurs when a wave bounces back after striking something.

1. b - refraction 2. d - crest 3. a - echo 4. d - vibrations 5. d - change direction 6. a - medium 7. b - energy 8. a - transverse waves 9. c - air10. d - bounces back11. false12. true13. true14. false15. false16. Refl ection occurs when a wave bounces back after striking something.17. Examples of transverse waves include light, radio waves, and microwaves.18. Most waves are produced by vibrations in moving objects or other matter.19. Sound can travel through solids, liquids, and gases.20. A wave is a traveling disturbance that carries energy through matter or space.


In Your Own Words (p. 20)

Writing Activity (p. 20)

Vocabulary (p. 19 )

Answer Key to Student Activities

1. wave 2. vibration 3. medium 4. transverse wave 5. longitudinal wave 6. amplitude 7. wavelength 8. frequency 9. refl ection10. refraction

Tennis Ball

Thrown straight down Thrown at angle

Directly above mirror Angled light

Light

Waves and Mediums (p. 21)1. Light cannot travel through the solid (the table top).2. Sound can travel through the air because the snap of the fi ngers could be heard. Sound could also travel through the solid such as the table top or desk top because the partner could hear the scratching. Sound also travels through water. 3. A sound wave is a longitudinal wave and a light wave is a transverse wave. A sound wave can travel through a solid whereas a light wave cannot.

Wave Characteristics (p. 22-23)1. Examples of transverse waves include light, radio waves and microwaves.2. In a transverse wave the particles move across, or perpendicular, to the direction the wave is traveling.3. A sound wave is an example of a longitudinal wave. 4. In a longitudinal wave, particles of the medium vibrate back and forth, parallel to the direction the wave is moving.

Experimenting with Refl ection (p. 24-25)

1. Refl ection is the process of an object or a wave bouncing back after making contact with an object it can’t pass through.2. According to the law of refl ection, the angle of incidence equals the angle of refl ection. In other words, the angle at which light bounces off a surface is equal to the angle at which it hits the surface.3. Both the light and the tennis ball refl ected straight up when directed straight down. The light and the tennis ball were refl ected at an angle when directed at an angle.4. The light would be refl ected in different directions when it hit the crumpled aluminum foil.

If you have ever used a microwave oven, sailed on the ocean, or been in an earthquake, you have experienced waves. A wave is a traveling disturbance that carries energy through matter or energy through matter or energyspace. Energy, often in the form of vibrations,is necessary to produce waves. A medium is the substance, or matter, through which a wave travels. Liquids, solids, and gases are all mediums. Light waves, microwaves, and radio waves are transverse waves. Sound waves are an example of longitudinal waves. Refl ection occurs when a wave bounces back after striking something. An echo involves the refl ection of a sound wave. Waves usually travel in straight lines, but when they pass from one medium into another, they change direction in a process called refraction.

1. Examples include sound waves, which enable you to listen to music and hear someone’s voice, and light waves which enables us to see.2. The crest is the highest point on a transverse wave and the trough is the lowest point.3. Refraction is the process of a wave bending as it passes from one medium to another.

Pre-TestCircle the best answer for each of the following questions.

1. A wave is a traveling disturbance that carries:

2. Waves are often created by the back and forth movements of matter called:

3. We most commonly hear sound waves that travel through:

4. The substance or matter through which a wave travels is a:

5. Light and electromagnetic waves are examples of:

6. The highest point on a transverse wave is called its:

7. Refl ection occurs when a wave strikes something and:

8. The refl ection of a sound wave is called a(n):

9. When waves pass from one medium into another they:

10. When you look at a pencil in a glass of water, the reason it looks bent is due to:

a. water vapor b. water vapor b. water vapor energy c. energy c. energy matter d. matter d. matter only light

a. energy units b. photons c. accelerations d. vibrations

a. Earth’s core b. ocean water c. ocean water c. ocean water air d. plasma

a. medium b. space c. fi eld d. fi eld d. fi eld magnetosphere

a. transverse waves b. longitudinal waves c. sound waves d. seismic waves

a. trough b. amplitude c. crescent crescent crescent d. crest

a. penetrates it b. saturates it c. is saturates it c. is saturates it absorbed d. bounces back

a. bounce back b. burn c. stop d. change direction

a. defl ection b. refraction c. absorption d. electromagnetism

a. echo b. accident c. misdirection d. transmission

Visual Learning Company

Page

14 The Nature of Waves

Name

Write a short answer for each of the following.

Pre-Test

11.

12.

13.

14.

15.

Write true or false next to each statement.

16. What is a wave?

17. How are waves commonly produced?

18. List the three mediums through which sound can travel.

19. Give an example of a transverse wave.

20. What is refl ection?

Energy is not needed to produce waves.

Sound cannot travel through water.

Light does not need a medium through which to travel.

All waves have the same wavelength.

A wave fl ows through matter but does not actually move it.


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Name

Circle the best answer for each of the following questions.

Post-Test

1. When you look at a pencil in a glass of water, the reason it looks bent is due to:

a. defl ection b. refraction c. absorption d. electromagnetism

2. The highest point on a transverse wave is called its:

a. trough b. amplitude c. crescent crescent crescent d. crest

3. The refl ection of a sound wave is called a(n):

a. echo b. accident c. misdirection d. transmission

4. Waves are often created by the back and forth movements of matter called:

a. energy units b. photons c. accelerations d. vibrations

5. When waves pass from one medium into another they:

6. The substance or matter through which a wave travels is a:

a. medium b. space c. fi eld d. magnetosphere

7. A wave is a traveling disturbance that carries:

a. water vapor b. water vapor b. water vapor energy c. energy c. energy matter d. only light

8. Light and electromagnetic waves are examples of:

a. transverse waves b. longitudinal waves c. sound waves d. seismic waves

9. We most commonly hear sound waves that travel through:

a. Earth’s core b. ocean water c. ocean water c. ocean water air d. plasma

10. Refl ection occurs when a wave strikes something and:

a. penetrates it b. saturates it c. is saturates it c. is saturates it absorbed d. bounces back

a. bounce back b. burn c. stop d. change direction


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Name

Post-Test

Write a short answer for each of the following.

Write true or false next to each statement.


17. Give an example of a transverse wave.

18. How are most waves produced?

19. List the three mediums through which sound can travel.

20. What is a wave?

11.

12.

13.

14.

15.

All waves have the same wavelength.

Light does not need a medium through which to travel.

A wave fl ows through matter but does not actually move it.

Energy is not needed to produce waves.

Sound cannot travel through water.


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Name

After you watch the video, test your knowledge with these questions.

While you watch the video, answer these questions:

Video Review

1. ______________ transfer energy from place to place.

2. A ___________________ is a movement that repeatedly follows the same path.

3. A ________________ is the substance, or matter, through which a wave travels.

4. Sound waves are examples of ____________________ waves.

5. ________________ occurs when a wave bounces back after striking something.

1. What do you notice when this guitar string is plucked?

2. Describe how the waves in this rope move.

3. Which wave has a greater amplitude, wave A or wave B?

You Decide!

You Compare!

You Observe!

4. What do you hear after this person shouts?

You Observe!


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Name

VocabularyUse these words to fi ll in the blanks next to the sentences below.

1.

7.

2.

6.

8.

4.

5.

3.

9.

10.

Wo

rds

A travelling disturbance that carries energy through matter or space.

A repeated back and forth movement of matter; often necessary to produce waves.

A substance or matter through which a wave travels.

A type of wave in which particles move across or perpendicular to the direction the wave is traveling.

A type of wave in which particles of the medium vibrate back and forth.

The distance between a wave’s resting point and its trough or crest.

The distance between any two adjacent wave crests or any two adjacent wave troughs.

The number of complete waves that pass a point in a certain period of time.

Occurs when a wave bounces back after striking something.

Occurs when a wave passes from one medium into another and changes direction.

transverse wave

longitudinal wavevibrationmedium

wavelength wave

amplitude

frequencyrefl ection

refraction


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Name

2. What is the difference between the crest and trough of a transverse wave?

1. List two ways you benefi t from waves.

Use the correct word from above to complete the sentences in the following paragraph.

Writing Activity

In Your Own Words

3. What is refraction?

Wo

rds

Wo

rds

Wo

rds

If you have ever used a microwave oven, sailed on the ocean, or been in an earthquake, you

have experienced ____________. A wave is a traveling disturbance that carries

______________ through matter or space. Energy, often in the form of __________________,

is necessary to produce waves. A _________________ is the substance, or matter, through

which a wave travels. Liquids, solids, and _____________ are all mediums. Light waves,

microwaves, and radio waves are _______________________. Sound waves are an example

of __________________________. ____________________ occurs when a wave bounces

back after striking something. An ______________ involves the refl ection of a sound wave.

Waves usually travel in straight lines, but when they pass from one medium into another, they

change direction in a process called __________________.

longitudinal waveswavesenergyenergy

vibrationsmedium gasesgases

transverse waves refl ectionecho refraction


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Name

Waves and MediumsHave you ever laid your ear down on a table and heard sounds travel through the table? Or have you ever seen light shine through water? Both of these examples illustrate how waves can travel through different mediums. A medium is the substance, or matter, through which a wave travels. Liquids, solids, and gases are all mediums. In this activity you will experiment with light (a transverse wave) and sound (a longitudinal wave) to see how they travel through different mediums.

Materials: fl ashlight, table, glass beaker, and water

1. Obtain a fl ashlight.2. Begin by seeing if light travels through air. Turn off the lights and darken the room. Turn on the fl ashlight. Can its light be seen? Does light travel through air? Record your observations below in the table.3. Point the fl ashlight at a table top. Does the light pass through it? Record your observations in the table below.4. Fill a glass beaker with water. Darken the room. Hold the fl ashlight close to the side of the beaker and point it through the beaker. Does light go through the water? Record your observations.

Directions: LightLight

Directions: Sound

1. Snap your fi ngers. Can you hear the snap? Record your observations.2. Obtain a large beaker of water or fi sh tank full of water. Place your hand underwater and snap your fi ngers. Place your ear close to the surface of the water. Can you hear the sound travel through the water? Record your observations.3. Have your partner put their ear down fl at against a table top or desk top. Move to the opposite end of the table or desk and lightly scratch it. Can your partner hear your scratching? Record your observations.

Light

Sound

Air Liquid Solid

1. Which medium can light not travel through?

2. Which medium(s) can sound travel through? How do you know this?

3. How is a sound wave different from a light wave?

Questions:


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Name

Wave CharacteristicsBackground: Whenever you listen to music, use a fl ashlight, or warm something in a microwave oven, you are using waves. A wave is a traveling disturbance that carries energy through matter or space. Waves transfer energy from one place to another.

In this activity you will explore the characteristics of two different types of waves: transverse waves and longitudinal waves. In a transverse wave, the particles move across, or perpendicular to, the direction the wave is traveling. Light, radio waves, and microwaves are transverse waves. In a longitudinal wave, particles of the medium vibrate back and forth, parallel to the direction the wave is moving. Sound waves are examples of longitudinal waves. When a sound wave moves from left to right, air particles collide with other nearby air particles and form an area of compression. Then the fi rst set of air particles moves to the right. This leaves a space containing many fewer particles, called rarefaction.

Waves have several different characteristics or properties, including amplitude, wavelength, and frequency. Following is a brief description of these properties:

amplitude - distance between a wave’s resting point and trough or crest.wavelength - distance between any two adjacent crests or any two adjacent troughs.frequency - the number of complete waves that pass a given point in a certain period of time.

There are sketches of a transverse wave and longitudinal wave on the next page. On the transverse wave, identify the crest, trough, amplitude, and wavelength. On the longitudinal wave, label the compression, rarefaction, and wavelength.

Directions:


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Name

Wave Characteristics

Questions:

1. List two examples of transverse waves.

2. Describe the motion of particles in a transverse wave.

3. Give an example of a longitudinal wave.

4. Describe the motion of particles in a longitudinal wave.


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Experimenting with Refl ectionBackground: If you have ever played pool or tennis, you know how important it is to understand how balls bounce back after hitting something. Refl ection is the process of an object or a wave bouncing back after making contact with an object it can’t pass through. Light can also be refl ected. Whenever you look into a mirror, you are benefi ting from the refl ection of light.

When you throw a tennis ball straight down it bounces straight up. But, if you throw it at an angle, it bounces away at an angle. Light behaves similarly. The angle at which light hits an object is called the angle of incidence. The angle at which light bounces off an object is called the angle of refl ection. According to the law of refl ection, the angle of incidence equals the angle of refl ection. In other words, the angle at which light bounces off a surface is equal to the angle at which it hits the surface. In this activity you will experiment with the law of refl ection.

Materials: tennis ball fl ashlight (with narrow beam) or laser pointer mirror talcum power (baby powder)

Directions:

1. Work in pairs. Obtain a tennis ball. 2. Gently bounce a tennis ball straight down toward the fl oor. Observe how the tennis ball refl ects (bounces back). 3. There are four blank boxes on the following page. In the appropriate space, draw the path and angle at which the tennis ball was thrown and refl ected. 4. Now gently throw the ball at an angle and have your partner catch it. 5. In the appropriate space, draw the path and angle at which the tennis ball was thrown and refl ected. 6. Now obtain a fl ashlight with a narrow beam or a laser pointer and a mirror. 7. Lay the mirror fl at on a table. Turn off the lights. Gently create a fi ne dust cloud of talcum powder above the mirror. 8. Quickly turn on the fl ashlight and point it directly toward the mirror from above. Observe how the beam of light is refl ected. 9. In the appropriate space, draw the path of the beam of light.10. Turn off the lights. Once again create a fi ne dust cloud of talcum powder above the mirror.11. Direct the beam of light at an angle toward the mirror. Observe the refl ected beam of light.12. In the appropriate space, draw the path of the light beam and label the angle of incidence and refl ection.


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Experimenting with Refl ection

Tennis BallThrown straight down Thrown at angle

Directly above mirror Angled lightLight


2. Describe the law of refl ection.

3. How did light behave like the tennis ball?

4. What would happen to the refl ection of light if it hit a crumpled piece of aluminum foil?

Questions:


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Documents

TheNature of Waves - InfobaseFor instance, in space there is little or no medium. 41. And yet, light from the sun and stars travels through the vacuum of space all the way to Earth