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Refraction: Snell’s Law Refraction: Snell’s Law Example : Refraction through flat glass. Light traveling in air strikes a flat piece of uniformly thick.

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Presentation on theme: "Refraction: Snell’s Law Refraction: Snell’s Law Example : Refraction through flat glass. Light traveling in air strikes a flat piece of uniformly thick."— Presentation transcript:

1 Refraction: Snell’s Law Refraction: Snell’s Law Example : Refraction through flat glass. Light traveling in air strikes a flat piece of uniformly thick glass at an incident angle of 60°, as shown. If the index of refraction of the glass is 1.50, (a) what is the angle of refraction θ A in the glass; (b) what is the angle θ B at which the ray emerges from the glass?

2 Refraction: Snell’s Law Refraction: Snell’s Law Example : Apparent depth of a pool. A swimmer has dropped her goggles to the bottom of a pool at the shallow end, marked as 1.0 m deep. But the goggles don ’ t look that deep. Why? How deep do the goggles appear to be when you look straight down into the water?

3 If the angle of incidence is larger than this, no transmission occurs. This is called total internal reflection. Total Internal Reflection; Fiber Optics Total Internal Reflection; Fiber Optics

4 Conceptual Example 32-11: View up from under water. Describe what a person would see who looked up at the world from beneath the perfectly smooth surface of a lake or swimming pool.

5 Binoculars often use total internal reflection; this gives true 100% reflection, which even the best mirror cannot do. Total Internal Reflection; Fiber Optics Total Internal Reflection; Fiber Optics

6 Optical fibers also depend on total internal reflection; they are therefore able to transmit light signals with very small losses.

7 ConcepTest 32.4aRefraction I 1 air 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? 1) medium 1 2) medium 2 3) both the same 2

8 ConcepTest 32.4aRefraction I 1 air 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? 1) medium 1 2) medium 2 3) both the same 2 Follow-up: air 12? Follow-up: How does the speed in air compare to that in # 1 or # 2?

9 ConcepTest 32.4bRefraction 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? 1) n 1 > n 2 > n 3 2) n 3 > n 2 > n 1 3) n 2 > n 3 > n 1 4) n 1 > n 3 > n 2 5) none of the above

10 ConcepTest 32.4bRefraction 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? 1) n 1 > n 2 > n 3 2) n 3 > n 2 > n 1 3) n 2 > n 3 > n 1 4) n 1 > n 3 > n 2 5) none of the above

11 ConcepTest 32.5aGone Fishin’ I To shoot a fish with a gun, should you aim directly at the image, slightly above, or slightly below? 1) aim directly at the image 2) aim slightly above 3) aim slightly below

12 ConcepTest 32.5aGone 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? 1) aim directly at the image 2) aim slightly above 3) aim slightly below

13 ConcepTest 32.5bGone Fishin’ II 1) aim directly at the image 2) aim slightly above 3) aim slightly below To shoot a fish with a laser gun, should you aim directly at the image, slightly above, or slightly below?

14 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 32.5bGone Fishin’ II laser beam light from fish 1) aim directly at the image 2) aim slightly above 3) aim slightly below To shoot a fish with a laser gun, should you aim directly at the image, slightly above, or slightly below?

15 ConcepTest 32.6Parallel Lines An observer views two closely spaced lines through an angled piece of glass. To the observer, the lines appear: 1) shifted to the right 2) shifted to the left 3) spaced farther apart 4) spaced closer together 5) no change – same as before

16 shift to the left The light rays get refracted twice, so they remain parallel, but they shift to the left, as seen in the figure. Their relative spacing does not change, just the overall position. ConcepTest 32.6Parallel Lines An observer views two closely spaced lines through an angled piece of glass. To the observer, the lines appear: 1) shifted to the right 2) shifted to the left 3) spaced farther apart 4) spaced closer together 5) no change – same as before Follow-up: Follow-up: What happens when the top glass moves toward the bottom glass?


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