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

Transcription

1 CHAPTER The Nature of Light DIRECTED READING WORKSHEET Date Class As you read Chapter 9, which begins on page 218 of your textbook, answer the following 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'll have 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 fluorescent and incandescent lights using your spectroscope? Why or why 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 vibrating electric and magnetic fields. TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 57

2 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 are perpendicular to the direction in which the wave is traveling. 11. Light travels through a vacuum than 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 different can 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 electromagnetic spectrum 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

3 17. When you listen to AM radio, the sounds you hear are encoded in radio waves by varying the waves vary in of the waves. FM radio 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 carry pictures. 27. If you watch cable television, how is the television signal sent from a distant broadcast studio to your home? List the steps. Microwaves (p. 224) 28. Microwaves carry less energy than radio waves. True or False? (Circle one.) TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 59

4 Using the information given in Figure 6, complete the description of a microwave oven and then order the sentences from 1-5 to explain how it works. 29. a. Microwaves pass several b. The waves are directed into the a metal into the food. by 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 of the food. the temperature 30. Look at the Brain Food on page 224. Name four household items that use radio waves. 31. What does radar stand for? 32. How are microwaves in radar used? (Circle all that apply.) a. to detect heat b. to monitor airplane movement c. to calculate the speed of a car d. to help navigate ships at night 60 HOLT SCIENCE AND TECHNOLOGY

5 Infrared Waves (p. 225) Mark each of the following statements True or False. 33. Microwaves have shorter wavelengths than infrared waves. 34 Infrared radiation can make you feel warm. 35. The warmer something is, the more infrared radiation 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 you learned by answering the Mid-Section Review questions in your ScienceLog. 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 EM wave provides the energy necessary for photosynthesis? a. microwaves c. visible light b. infrared light d. ultraviolet light 40. Who is Roy G. Biv, and why should you remember his name? A Ultraviolet Light (p. 227) 41. Name two good effects of ultraviolet light. TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 61

6 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 by answering 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? sc sso C C.c a) C 0 Reflection (p. 229) 2. When you look in a mirror you see light that has been reflected twice. True or False? (Circle one.) 3. What is the law of reflection? 0 62 HOLT SCIENCE AND TECHNOLOGY

7 4. In Figure 13, the is the line perpendicular 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 to particles 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 to i be separated from the person's legs. This happens because your brain always interprets light as traveling in F. 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, u Diffraction (p. 233) 15. The of waves around barriers or through 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. A TEXAS EDITION, GRADE 8, UNIT 2 RESOURCES 63

8 17. Diffraction patterns are easier to see when they are made using a light 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 waves that combined to form it. 19. The result of interference is dimmer light. 20. Why do you not see constructive and destructive interference of white light? Use the information in Section 2 to answer the following questions. Choose the word in Column B that best matches the definition or example 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. interference particles of matter b. scattering 22. bending of light passing through an opening c. absorption 23. bending of a wave as it passes at an angle from d. diffraction one medium to another e. refraction 24. a wave bouncing off an object f. reflection 25. waves overlapping and combining 26. release of light energy by particles of matter that have absorbed energy Section Review (p. 234) Now that you've finished Section 2, review what you learned by answering the Section Review questions in your ScienceLog. Section 3: Light and Color (p. 235) 1. What is white light made of? 64 HOLT SCIENCE AND TECHNOLOGY