1 Chapter 5 Post‐Lecture Quiz 1. What is light? 1. 2. 3. 4. Light is a wave, like sound only much faster Light is like little bullets. Each one is a photon Light is the absence of dark A kind of energy we model with some of the properties of waves and some properties of particles 5. Light is the sensation you feel when hit by energy, visible or invisible 2. What is the electromagnetic spectrum? 1. Light of all different wavelengths 2. Light of all different energies 3. Radiation, some of which is dangerous, and some of which is harmless 4. All of the above 3. Put the following kinds of light in order, according to wavelength, short to long: 1. Visible light, ultraviolet (UV), infrared (IR), radio, microwaves, X rays, gamma rays 2. Gamma rays, X rays, UV, visible, IR, radio 3. X rays, UV, visible, IR, radio, gamma rays 4. UV, visible light, IR, gamma rays, X rays 4. We can’t see infrared, but we can perceive it as: 1. Heat 2. Radar 3. Sound 4. AM 5. FM 5. Which travels fastest? 1. X rays 2. Ultraviolet 3. Visible 4. Radio waves 5. They all travel at the same speed 6. Which is likely to originate from the hottest–most energetic–object? 1. Gamma rays 2. X rays 3. Ultraviolet 4. Visible 5. Radio waves 2 7. What happens to thermal radiation (a continuous spectrum) if you make the source hotter? 1. More energy comes out at all wavelengths 2. The peak of the spectrum‐energy curve (the wavelength at which most energy is emitted) shifts redward 3. The peak of the spectrum‐energy curve shifts blueward 4. 1 and 2 5. 1 and 3 8. How is the isotope 14 C different from 12 C? 1. It has more protons 2. It has more neutrons 3. It has more electrons 4. All of the above 5. None of the above 9. In what ways is an electron orbiting the nucleus of an atom different from a planet orbiting the Sun? 1. The central force is electromagnetic (+ and ‐charges attract), not gravity 2. Not all orbits are allowed–only certain sizes (they are quantized) 3. Because atomic orbits behave differently from “regular” orbits we call them orbitals 4. An electron can jump or make a transition from one orbital to another 5. All of the above 10. What can cause an electron to jump from a low‐energy orbital to a higher‐energy one? 1. A photon of light is emitted 2. A photon of light is absorbed 3. The atom changes color 4. None of the above 11. What’s the difference in what you see when visible light of different energies enters your eye: 1. You see a range of brightness 2. You see different colors 3. Your eye feels warm or cool 4. More energetic light makes you blink 5. None of the above 12. If all the colors (a continuous spectrum) pass through a gas, what kind of spectrum do you get? 1. Emission (bright lines) 2. Absorption (dark lines) 3. Continuous (all the colors of the rainbow) 4. Infrared 5. Ultraviolet 3 13. The visible spectrum of the sun is: 1. Emission (bright lines) 2. Absorption (dark lines) 3. Continuous (all the colors of the rainbow) 4. Doppler shifted 5. None of the above 14. Since each element has a different number of protons and electrons and a different pattern of orbitals, 1. Gasses made of different elements have different patterns of emission and absorption lines 2. Each element’s spectrum is unique 3. We can tell what a gas is made of from its spectrum, even if it is billions of miles away 4. All of the above 5. 1 and 2 15. Which is the hottest star? One that appears: 1. Orange 2. Red 3. Yellow 4. White, or bluish‐white 5. They are all the same temperature. They just look different colors 16. Consider different colored shirts. Which is hottest? One that appears: 1. Orange 2. Red 3. Yellow 4. White, or bluish‐white 5. They are all the same temperature. They just look different colors 17. What controls the color of a shirt, a planet, or anything that shines by reflecting light? 1. Its temperature 2. How well it reflects light of different colors 3. The color of the light hitting it 4. 2 and 3 5. 1, 2, and 3 18. By looking at the light of a hot, solid object, you can tell: 1. Its temperature 2. What it is made of 3. Both 1 and 2 4. Neither 1 nor 2, without some additional information 4 19. If a source of light is moving away from you, all the wavelengths are: 1. Shifted to shorter wavelengths (Doppler shifted) 2. Shifted to longer wavelengths (Doppler shifted) 3. Red shifted 4. 2 and 3 5. None of the above 20. If a distant galaxy has a substantial redshift (as viewed from our galaxy), then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milky Way Galaxy. 1. Yes, and the redshifts would be the same. 2. Yes, but we would measure a higher redshift than they would. 3. Yes, but we would measure a lower redshift than they would. 4. No, they would not measure a redshift toward us. 5. No, they would measure a blueshift.