Quiz 8

1. Not graded

2. Color and Temperature Why does an opaque and dense object (such as metal) first glow white before it glows blue when it is heated? 1. Becuase humans tend to associate cold with blue. 2. Because the metal is not a perfect blackbody. 3. As you heat the metal, its blackbody curve shifts until the peak is at a green wavelength. What humans call white corresponds to the special combination of intensity of green photons along with fewer red and blue photons that the blackbody curve specifies. 4. Before the metal glows blue, it emits white photons because this is the emission spectra of that metal at that temperature.

2. Color and Temperature Why does an opaque and dense object (such as metal) first glow white before it glows blue when it is heated? 1. Because humans tend to associate cold with blue. 2. Because the metal is not a perfect blackbody. 3. As you heat the metal, its blackbody curve shifts until the peak is at a green wavelength. What humans call white corresponds to the special combination of intensity of green photons along with fewer red and blue photons that the blackbody curve specifies. 4. Before the metal glows blue, it emits white photons because this is the emission spectra of that metal at that temperature.

3. Spectrum 3 The image below is the spectrum discussed in class. Suppose Earth's atmosphere contained only nitrogen atoms. What would change? 1. The peak in curve B would be less pronounced. 2. All of the curves would increase in amplitude and their peak location would shift to the left. 3. There would be fewer dips in curve C. The locations of the dips would correspond to the location of the empty spots in the spectra that one would measure of light from a blackbody passed through a cloud of nitrogen gas. 4. Curve B would look much more like curve C. 5. All of the curves would increase in amplitude and their peak location would shift to the right.

3. Spectrum 3 The image below is the spectrum discussed in class. Suppose Earth's atmosphere contained only nitrogen atoms. What would change? 1. The peak in curve B would be less pronounced. 2. All of the curves would increase in amplitude and their peak location would shift to the left. 3. There would be fewer dips in curve C. The locations of the dips would correspond to the location of the empty spots in the spectra that one would measure of light from a blackbody passed through a cloud of nitrogen gas. 4. Curve B would look much more like curve C. 5. All of the curves would increase in amplitude and their peak location would shift to the right.

4. You ought to be in pictures How much larger is a raw image of 900x900 pixels than one with 300x300 pixels? That is, how many more pixels are in the 900x900 image?

4. You ought to be in pictures How much larger is a raw image of 900x900 pixels than one with 300x300 pixels? That is, how many more pixels are in the 900x900 image?

5. Driving on the lawn In the following image, what happens to the wheels when they hit the grass, and why? 1. The wheels turn as in case (a). When the leading wheel hits the grass, it speeds up while the trailing wheel keeps at the same speed. While the trailing wheel is on the sidewalk, the axle turns as shown in (a). 2. The wheels turn as in case (a). When the leading wheel hits the grass, it slows down while the trailing wheel keeps at the same speed. While the trailing wheel is on the sidewalk, the axle turns as shown in (a). 3. The wheels turn as in case (c). When the leading wheel hits the grass, it slows down while the trailing wheel keeps at the same speed. While the trailing wheel is on the sidewalk, the axle turns as shown in (c). 4. The wheels turn as in case (b). When the leading wheel hits the grass, it slows down at the same rate as the trailing wheel. While the trailing wheel is on the sidewalk, the axle turns as shown in (a).

5. Driving on the lawn In the following image, what happens to the wheels when they hit the grass, and why? 1. The wheels turn as in case (a). When the leading wheel hits the grass, it speeds up while the trailing wheel keeps at the same speed. While the trailing wheel is on the sidewalk, the axle turns as shown in (a). 2. The wheels turn as in case (a). When the leading wheel hits the grass, it slows down while the trailing wheel keeps at the same speed. While the trailing wheel is on the sidewalk, the axle turns as shown in (a). 3. The wheels turn as in case (c). When the leading wheel hits the grass, it slows down while the trailing wheel keeps at the same speed. While the trailing wheel is on the sidewalk, the axle turns as shown in (c). 4. The wheels turn as in case (b). When the leading wheel hits the grass, it slows down at the same rate as the trailing wheel. While the trailing wheel is on the sidewalk, the axle turns as shown in (a).

6. Chromatic aberration What causes chromatic aberration? 1. The fact that light at different frequencies bends a different amount when it goes from air into glass. 2. The fact that all electromagnetic radiation travels at the speed of light in a vacuum. 3. The fact that when a light beam strikes a mirror, it is reflected at the same angle with respect to the normal as its incident angle. 4. The fact that each photon has an energy that is given by Plank's Law.

6. Chromatic aberration What causes chromatic aberration? 1. The fact that light at different frequencies bends a different amount when it goes from air into glass. 2. The fact that all electromagnetic radiation travels at the speed of light in a vacuum. 3. The fact that when a light beam strikes a mirror, it is reflected at the same angle with respect to the normal as its incident angle. 4. The fact that each photon has an energy that is given by Plank's Law.

7. Light bending 2 If white represents air and blue represents water, which way does the beam go when it enters the water? 1. C 2. B 3. A

7. Light bending 2 If white represents air and blue represents water, which way does the beam go when it enters the water? 1. C 2. B 3. A

8. Lens Suppose you have a single lens from a pair of eyeglasses that is 3 inches in diameter. How many more photons hit this lens per second than would hit a lens that is only 1.5 inches in diameter? 1. 4 times 2. 8 times 3. 2 times times

8. Lens Suppose you have a single lens from a pair of eyeglasses that is 3 inches in diameter. How many more photons hit this lens per second than would hit a lens that is only 1.5 inches in diameter? 1. 4 times 2. 8 times 3. 2 times times

9. Refraction When light is incident on a surface, refraction occurs when 1. it “bounces off” and changes frequency. 2. it “bounces off” at an angle (measured from the normal) equal to the incident angle. 3. it enters the second medium and changes frequency. 4. it “bounces off” at an angle (measured from the normal) greater than the incident angle. 5. it enters the second medium and changes direction.

9. Refraction When light is incident on a surface, refraction occurs when 1. it “bounces off” and changes frequency. 2. it “bounces off” at an angle (measured from the normal) equal to the incident angle. 3. it enters the second medium and changes frequency. 4. it “bounces off” at an angle (measured from the normal) greater than the incident angle. 5. it enters the second medium and changes direction.

10. Telescopes Why is the Hubble Space Telescope in orbit of Earth? 1. Maintenance on the telescope is easier to do in Earth orbit than on the Earth’s surface. 2. To get away from human-generated electromagnetic interference. 3. To detect X-rays, which cannot penetrate the Earth’s atmosphere. 4. To eliminate the distorting effect of the Earth’s atmosphere.

10. Telescopes Why is the Hubble Space Telescope in orbit of Earth? 1. Maintenance on the telescope is easier to do in Earth orbit than on the Earth’s surface. 2. To get away from human-generated electromagnetic interference. 3. To detect X-rays, which cannot penetrate the Earth’s atmosphere. 4. To eliminate the distorting effect of the Earth’s atmosphere.

11. Objective lens What is the primary purpose of the objective lens in a telescope? 1. To gather light 2. To isolate visible light from other electromagnetic radiation 3. To correct for chromatic aberration 4. To magnify the image

11. Objective lens What is the primary purpose of the objective lens in a telescope? 1. To gather light 2. To isolate visible light from other electromagnetic radiation 3. To correct for chromatic aberration 4. To magnify the image

12. Camera lens Why does a camera with a bigger lens give you a more detailed image? Select the best answer. 1. More photons are used to create the image. More photons means more detail because there is less chromatic aberration. 2. Fewer photons are used to create the image. Fewer photons means more detail because there is less chromatic aberration. 3. More photons are used to create the image. More photons means more detail for the same reason you could draw a more detailed object using many dots versus fewer dots. 4. Fewer photons are used to create the image. Fewer photons means more detail because there is less interference among photons.

12. Camera lens Why does a camera with a bigger lens give you a more detailed image? Select the best answer. 1. More photons are used to create the image. More photons means more detail because there is less chromatic aberration. 2. Fewer photons are used to create the image. Fewer photons means more detail because there is less chromatic aberration. 3. More photons are used to create the image. More photons means more detail for the same reason you could draw a more detailed object using many dots versus fewer dots. 4. Fewer photons are used to create the image. Fewer photons means more detail because there is less interference among photons.

13. Normal In the diagram a water droplet is shown along with a light beam that hits the droplet's surface. Which line best represents the normal to the droplet's surface at the point where the light beam hits the droplet? 1. A 2. B 3. C

13. Normal In the diagram a water droplet is shown along with a light beam that hits the droplet's surface. Which line best represents the normal to the droplet's surface at the point where the light beam hits the droplet? 1. A 2. B 3. C

14. Refraction off of a water droplet In the diagram, a water droplet is shown. A beam of light is shown to hit the water droplet's surface. Which path best represents the path of the beam of light? 1. P1 2. P2 3. P3

14. Refraction off of a water droplet In the diagram, a water droplet is shown. A beam of light is shown to hit the water droplet's surface. Which path best represents the path of the beam of light? 1. P1 2. P2 3. P3

15. Refraction 3 This diagram was used in class. Suppose the pupil sent out a photon along the direction of the dotted line. Where would the photon hit the coin? 1. At the starred point. 2. At the center of the coin. 3. At the outside edge of the coin.

15. Refraction 3 This diagram was used in class. Suppose the pupil sent out a photon along the direction of the dotted line. Where would the photon hit the coin? 1. At the starred point. 2. At the center of the coin. 3. At the outside edge of the coin.

15. Refraction 3 This diagram was used in class. Suppose the pupil sent out a photon along the direction of the dotted line. Where would the photon hit the coin? 1. At the starred point. 2. At the center of the coin. 3. At the outside edge of the coin.