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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.
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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.)
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Name Date Class
Chapter 9 Directed Reading, continued
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.)
TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 59
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Name Date Class
Chapter 9 Directed Reading, continued
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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Chapter 9 Directed Reading, continued
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.
TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 61
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Chapter 9 Directed Reading, continued
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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Chapter 9 Directed Reading, continued
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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Chapter 9 Directed Reading, continued
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?
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