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Refraction: Snell ’ s Law

Refraction: Snell ’ s Law. Example : Refraction through flat glass.

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Refraction: Snell ’ s Law

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  1. 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 θA in the glass; (b) what is the angle θB at which the ray emerges from the glass?

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

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

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

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

  8. air air 1 ConcepTest 32.4aRefraction 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? 1) medium 1 2) medium 2 3) both the same The greater the difference in the speed of light between the two media, the greater the bending of the light rays. 2 Follow-up:How does the speed in air compare to that in #1 or #2?

  9. 1 2 3 ConcepTest 32.4bRefraction II 1) n1 > n2 > n3 2) n3 > n2 > n1 3) n2 > n3 > n1 4) n1 > n3 > n2 5) none of the above 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?

  10. 1 2 3 ConcepTest 32.4bRefraction II 1) n1 > n2 > n3 2) n3 > n2 > n1 3) n2 > n3 > n1 4) n1 > n3 > n2 5) none of the above 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? The rays are bent toward the normal when crossing into #2, so n2 > n1. But rays are bent away from the normal when going into #3, so n3 < n2. How to find the relationship between #1 and #3? Ignore medium #2! So the rays are bent away from the normal if they would pass from #1 directly into #3. Thus, we have: n2 > n1 > n3 .

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

  12. ConcepTest 32.5a Gone Fishin’ I 1) aim directly at the image 2) aim slightly above 3) aim slightly below To shoot a fish with a gun, should you aim directly at the image, slightly above, or slightly below? Due to refraction, the image will appear higher than the actual fish, so you have to aimlower to compensate.

  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 from fish laser beam 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? The light from the laser beam will also bend when it hits the air-water interface, so aimdirectly at the fish.

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

  16. ConcepTest 32.6Parallel Lines 1) shifted to the right 2) shifted to the left 3) spaced farther apart 4) spaced closer together 5) no change – same as before An observer views two closely spaced lines through an angled piece of glass. To the observer, the lines appear: 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. Follow-up:What happens when the top glass moves toward the bottom glass?

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