ConcepTest 6.4aRefraction I Parallel light rays cross interfaces from air into two different media, 1 and 2, as shown in the figures below. In which of the media is the light traveling faster? a) medium 1 b) medium 2 c) both the same 2

ConcepTest 6.4aRefraction I The greater the difference in the speed of light between the two media, the greater the bending of the light rays. Parallel light rays cross interfaces from air into two different media, 1 and 2, as shown in the figures below. In which of the media is the light traveling faster? a) medium 1 b) medium 2 c) both the same 2 Follow-up: air 12? Follow-up: How does the speed in air compare to that in 1 or 2? 2

ConcepTest 6.4bRefraction II Parallel light rays cross interfaces from medium 1 into medium 2 and then into medium 3. What can we say about the relative sizes of the index of refraction of these media? a) n 1 > n 2 > n 3 b) n 3 > n 2 > n 1 c) n 2 > n 3 > n 1 d) n 1 > n 3 > n 2 e) none of the above

ConcepTest 6.4bRefraction II bent toward the normal n 2 > n 1 bent away from the normaln 3 n 1 > n 3 The rays are bent toward the normal when crossing into #2, so n 2 > n 1. But rays are bent away from the normal when going into #3, so n 3 n 1 > n Parallel light rays cross interfaces from medium 1 into medium 2 and then into medium 3. What can we say about the relative sizes of the index of refraction of these media? a) n 1 > n 2 > n 3 b) n 3 > n 2 > n 1 c) n 2 > n 3 > n 1 d) n 1 > n 3 > n 2 e) none of the above

ConcepTest 6.5aGone Fishin’ I To shoot a fish with a gun, should you aim directly at the image, slightly above, or slightly below? a) aim directly at the image b) aim slightly above c) aim slightly below

ConcepTest 6.5aGone Fishin’ I higher aimlower Due to refraction, the image will appear higher than the actual fish, so you have to aim lower to compensate. To shoot a fish with a gun, should you aim directly at the image, slightly above, or slightly below? a) aim directly at the image b) aim slightly above c) aim slightly below

ConcepTest 6.5bGone Fishin’ II a) aim directly at the image b) aim slightly above c) aim slightly below To shoot a fish with a laser gun, should you aim directly at the image, slightly above, or slightly below?

light bend aim directly at the fish The light from the laser beam will also bend when it hits the air-water interface, so aim directly at the fish. ConcepTest 6.5bGone Fishin’ II laser beam light from fish a) aim directly at the image b) aim slightly above c) aim slightly below To shoot a fish with a laser gun, should you aim directly at the image, slightly above, or slightly below?

ConcepTest 6.5Heat Insulation Imagine you are an alien from another planet with infrared eyes. What do you see when you look around the room? a) Bright spots where the bodies are and dark elsewhere. b) Dark spots where the bodies are and bright elsewhere. c) The same as what we see, only everything looks red. d) The same as what we see, except that red is invisible.

emit infrared radiation sources as bright spots Bodies are sources of heat and therefore emit infrared radiation. An alien with an instrument to detect infrared would see these sources as bright spots. ConcepTest 6.5Heat Insulation Imagine you are an alien from another planet with infrared eyes. What do you see when you look around the room? a) Bright spots where the bodies are and dark elsewhere. b) Dark spots where the bodies are and bright elsewhere. c) The same as what we see, only everything looks red. d) The same as what we see, except that red is invisible. Infrared photo of a building to check the heat insulation – where are the problem spots in this case?

ConcepTest 6.6Superman a) Yes, no problem b) Nope, he can’t c) Need more information Since Superman is from the planet Krypton his eyes are sensitive to the entire electromagnetic spectrum. Does that mean he can use x-ray vision to see that Lois Lane is being kidnapped in the other room?

receivesend X-ray vision means that Superman’s eyes can receive x-rays, but not send them! So what would have to happen for him to see Lois Lane being kidnapped? ConcepTest 6.6Superman a) Yes, no problem b) Nope, he can’t c) Need more information Since Superman is from the planet Krypton his eyes are sensitive to the entire electromagnetic spectrum. Does that mean he can use x-ray vision to see that Lois Lane is being kidnapped in the other room?