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Back Print Name Class Date Skills Worksheet Critical Thinking Now You See It, Now You Don’t Prime Time Interviews Announcer: Captain Reginald P. Nutt, hero and explorer, has just returned from an expedition in the Sahara Desert. We are fortunate enough to conduct the first live interview with him. Kara Little: Captain P. Nutt, I understand that you did not finish your journey across the Sahara. Captain P. Nutt: Quite right. If it weren’t for those pesky mirages, I would have completed the journey. Kara Little: Optical illusions kept you from finishing your expedition? Captain P. Nutt: It may sound silly, but imagine constantly seeing pools of water in a hot desert only to find out there really is no water. It is enough to drive anyone nuts! Kara Little: What causes these illusions? Captain P. Nutt: Changes in air temperature cause changes in air density. Mirages are caused when light is bent as it passes through layers of air that have different densities. I’ve also seen mirages in extremely cold places, like Antarctica. Kara Little: Well, that’s all the time we have today. Tune in next week for more. USEFUL TERMS mirage an optical illusion in which a distant object appears to be nearby optical illusion something which deceives the eye by false or unreal appearances COMPREHENDING IDEAS 1. Is light refracted when you see a mirage? Explain your answer. Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 62 The Nature of Light Back Print Name Class Date Critical Thinking continued 2. Captain P. Nutt claims to have seen mirages in extremely cold climates. Do you think this is possible? Why or why not? MAKING COMPARISONS 3. The refraction of light causes many interesting visual displays, including rainbows. How is the formation of a rainbow different from the formation of a mirage? 4. Objects sometimes appear bent or disconnected when they are partially placed in water. How is the formation of this illusion similar to the formation of a mirage? DEMONSTRATING REASONED JUDGMENT 5. Captain P. Nutt is planning his next scientific expedition to the forests and swamps of Louisiana. Give two reasons why he might not see mirages there. Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 63 The Nature of Light Print TEACHER RESOURCE PAGE 17. 18. 19. 20. 21. Diffraction: a change in the direction of a wave when the wave finds an obstacle or an edge, such as an opening. Example: Shadows appear slightly blurry at the edges. Interference: the combination of two or more waves that results in a single wave. Example: When light of one wavelength shines through two slits onto a screen a series of bright and dark bands will appear. FIONA, PRIVATE EYE 1. a. normal; b. angle of incidence; c. reflected beam; d. incident beam; e. angle of reflection Light source Normal Incident beam Reflected beam Angle of incidence Angle of reflection Mirror 2. _ _ _ _ 22. Refraction: the bending of a wave as the wave passes between two substances in which the speed of the wave differs. Example: a straw placed in a glass of water appears bent. _ 16. Scattering: an interaction of light with matter that causes light to change its energy, direction of motion, or both. Example: Scattering of blue light makes the sky look blue. _ 15. A C B D C Gamma rays are used to treat some forms of cancer and are used to kill harmful bacteria in foods. Two uses for radio waves are the broadcasting of radio signals and the broadcasting of television signals. Frost is translucent, so the light traveling through it is scattered as it passes through. time distance speed time; time 54,900,000 km 300,000 km/s; time 183 s (or 3.05 min) An answer to this exercise can be found at the end of this book. The tern sees the fish in the wrong place because light refracts as it passes from the water to the air. This creates an optical illusion for the tern. My brother’s conclusion is wrong because he is confusing mixing of light (color addition) with mixing of pigments (color subtraction). Sunshades keep the interior of cars from getting very hot because sunshades reflect light that is transmitted through the glass window of the car. The light reflects back out the window, so the light cannot warm the air or seats inside the car. a. refraction; b. absorption and scattering; c. reflection _ 9. 10. 11. 12. 13. 14. ____ _ Reinforcement _ LIGHT INTERACTIONS _ _ _ _ _ Absorption: in optics, the transfer of light energy to particles of matter. Example: Due to absorption (and scattering), the beam of a flashlight appears dimmer the further it is from the flashlight. _ Answers will vary. Sample answers: Reflection: the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through. Example: A green sweater looks green because green light is reflected off it. _ Back Fiona Jorge Charles Tamika wall 3. Fiona can see Jorge. Critical Thinking 1. Yes; light rays bend as they pass through air layers of different densities because the speed of light changes. Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 126 The Nature of Light Back Print TEACHER RESOURCE PAGE 2. Sample answer: Yes, it is possible because the temperature of the ground is colder than the air above it, creating air layers of different densities. The light is bent as it passes through the different layers and can create a mirage. 3. Sample answer: Rainbows are formed when light is refracted by water droplets instead of through layers of air, as in a desert mirage. 4. Sample answer: Both are formed by the refraction of light as it passes through mediums of different densities. An object appears bent in water because light bends as it passes from air to water. A mirage appears when light is bent as it passes through air layers of different densities. 5. Sample answer: The temperatures in this area are not extreme enough to cause the changes in air density required for mirages. In addition, the trees may block the sunlight that is needed to create a mirage. Section Quizzes SECTION: WHAT IS LIGHT? 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. B C A D B A D A D B SECTION: THE ELECTROMAGNETIC SPECTRUM 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. D C B F E G A D C A SECTION: INTERACTIONS OF LIGHT WAVES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. A F D E B C C D A B SECTION: LIGHT AND COLOR 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. D E A C B C B A A B Chapter Test A 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. C C D C E F A B C D G E F 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. D A B C G C A B A C B C Chapter Test B 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. scattering opaque absorption interference transparent B A D A D Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 127 The Nature of Light