directed reading worksheet the nature of light...bow light. 9. makes the sky appear blue. 10. air...

$: DIRECTED READING WORKSHEET The Nature of Light...bow light. 9. Makes the sky appear blue. 10. Air particles absorb some of the energy from a light, making it less bright. Refraction$
DIRECTED READING WORKSHEET• The Nature of Light

Name Date

CHAPTER

Class

•

As you read Chapter 9, which begins on page 218 of your textbook, answer thefollowing questions.

What on Earth...? (p. 218)

1. The picture on p. 218 is of an ordinary object. What is it?

2. Why does the object look so different?

Pre-Reading Questions (P. 218)

Answer these questions in your ScienceLog now. Then later, you'llhave a chance to revise your answers based on what you've learned.

Start-Up Activity (p. 219)

3. Do you think you will be able to tell the difference between fluo-rescent and incandescent lights using your spectroscope? Why orwhy not?

Section 1: What Is Light? (p. 220)

4. Name at least two things that produce light.

Light Is an Electromagnetic Wave (p. 220)

5. Unlike sound, light does not need a through which to travel.

6. A(n) wave is composed of vibratingelectric and magnetic fields.

TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 57

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Chapter 9 Directed Reading, continued

Mark each of the following statements True or False.

7. A field can exert a push or a pull on an object.8. Fields are made of matter.

9 Light travels more slowly than sound.10. Light waves are considered longitudinal waves

because the electric and magnetic fields areperpendicular to the direction in which the waveis traveling.

11. Light travels through a vacuumthan through a medium such as air, water, or glass.

The Electromagnetic Spectrum (p. 221)

12. What does the bee in Figure 2 see that you can't see?

13. The entire range of EM waves is called the

Characteristics of EM Waves (p. 221)

14. EM waves with differentcan travel at the same speed as long as their are also different.

Radio Waves (p. 222)

15. Name at least four kinds of EM waves.

16. Take a moment to look at the diagram of the electromagneticspectrum on pages 222 and 223. We can see most of the EM

waves in our world. True or False? (Circle one.)

58 HOLT SCIENCE AND TECHNOLOGY

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17. When you listen to AM radio, the sounds you hearare encoded in radio waves by varying the

of the waves. FM radio

waves vary in

Mark each of the following statements AM or FM.

18. Waves can travel a longer distance.19. Waves have shorter wavelengths.

20. Waves can reflect off the ionosphere.

21. Waves can encode more information.22. Music sounds better.23. Waves carry the pictures you see on

television.24 Waves carry the sounds you hear on

television.25. Television stations use

to carry sound.

26. They use to carrypictures.

27. If you watch cable television, how is the television signalsent from a distant broadcast studio to your home? List thesteps.

Microwaves (p. 224)

28. Microwaves carry less energy than radio waves. True or False?(Circle one.)


•

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Using the information given in Figure 6, complete the description ofa microwave oven and then order the sentences from 1-5 to explainhow it works.

29. a. Microwaves pass several into the food.

b. The waves are directed into the bya metal

c. The energy of the waves causes water molecules

inside the food to d. Microwaves are created by a device called a , which accelerates

charged particles.e. The vibration of molecules

the temperatureof the food.

30. Look at the Brain Food on page 224. Name four household itemsthat use radio waves.

31. What does radar stand for?

32. How are microwaves in radar used? (Circle all that apply.)a. to detect heatb. to monitor airplane movementc. to calculate the speed of a card. to help navigate ships at night •

•


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Infrared Waves (p. 225)

Mark each of the following statements True or False.

33. Microwaves have shorter wavelengths than infraredwaves.

34 Infrared radiation can make you feel warm.35. The warmer something is, the more infrared radia-

tion it gives off.36. With the right equipment, you can "see" in the dark

using infrared radiation.

Mid-Section Review (p. 225)

Now that you've finished the first part of Section 2, review what youlearned by answering the Mid-Section Review questions in yourScienceLog.

Visible Light (p. 226)

37. The shortest wavelengths of visible light, which carry the energy, are seen as

light.

38. The longest wavelengths of visible light are seen as

light.

39. Look at the Biology Connection on page 226. What kind of EMwave provides the energy necessary for photosynthesis?a. microwaves c. visible lightb. infrared light d. ultraviolet light

40. Who is Roy G. Biv, and why should you remember his name?

AAA

Ultraviolet Light (p. 227)

41. Name two good effects of ultraviolet light.


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42. Name two bad effects of ultraviolet light.

X Rays and Gamma Rays (p. 228)

43. How are X rays useful to doctors?

44. Why do you need to use a lead-lined cover when getting an X ray?

45. Which of the following is NOT true of gamma rays?a. They are used to treat some forms of cancer.b. They carry less energy than X rays.c. They penetrate materials easily.d. In cancer treatments, they can kill healthy cells.

Section Review (p. 228)

Now that you've finished Section 1, review what you learned byanswering the Section Review questions in your ScienceLog.

Section 2: Interactions of Light Waves (p. 229)

1. How is the special layer of cells in the back of a cat's eyes useful?

Reflection (p. 229)

2. When you look in a mirror you see light that has been reflectedtwice. True or False? (Circle one.)

3. What is the law of reflection?


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4. In Figure 13, the is the lineperpendicular to the mirror's surface.

5. What kind of surface allows you to see your reflection?

Absorption and Scattering (p. 230)

Decide if each of the following refer to scattering or absorption.Write S for scattering and A for absorption.

6. The transfer of energy carried by light waves toparticles of matter. Particles of matter that have absorbed energy release

light energy.8. On a dark night, you can see objects outside of a

bow light.9. Makes the sky appear blue.

10. Air particles absorb some of the energy from a light,making it less bright.

Refraction (p. 231)

1 1 . Refraction is caused by a change in the of light as it passes from one medium to another.

12. The speed of light traveling through glass is slower than the

-t. speed of light traveling through air. True or False? (Circle one.)

.5; 13. When you look at someone's feet underwater, they seem toi be separated from the person's legs. This happens because

your brain always interprets light as traveling inF. lines.

.=, 14. Color separation happens in refraction because light waves with>. long wavelengths are bent more than light waves with short

Cd)

.-6 wavelengths. True or False? (Circle one.)0,05-..u Diffraction (p. 233)

15. The of waves around barriers orthrough openings is called diffraction.

16. The greatest amount of diffraction occurs when the barrier or

• opening is the same size as or than the wavelength of the light passing through it.


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17. Diffraction patterns are easier to see when they are made using alight source of a single color. True or False? (Circle one.)

Interference (p. 233)

18. The new wave that results from interference has a greater amplitude than the individual wavesthat combined to form it.

19. The result of interference isdimmer light.

20. Why do you not see constructive and destructive interference ofwhite light?

Use the information in Section 2 to answer the following questions.Choose the word in Column B that best matches the definition orexample in Column A, and write your answer in the space provided.

Column A Column B

21. transfer of energy carried by light waves to a. interferenceb. scatteringc. absorption

d. diffractione. refractionf. reflection

particles of matter

22. bending of light passing through an opening

23. bending of a wave as it passes at an angle fromone medium to another

24. a wave bouncing off an object

25. waves overlapping and combining

26. release of light energy by particles of matter thathave absorbed energy

Section Review (p. 234)

Now that you've finished Section 2, review what you learned byanswering the Section Review questions in your ScienceLog.

Section 3: Light and Color (p. 235)

1. What is white light made of?


directed reading worksheet the nature of light...bow light. 9. makes the sky appear blue. 10. air...

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