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Unformatted text preview: nguyen (jmn727) homework 35 Turner (59070) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points The index of refraction of a transparent liquid (similar to water but with a different index of refraction) is 1 . 25. A flashlight held under the transparent liquid shines out of the transpar- ent liquid in a swimming pool. This beam of light exiting the surface of the transparent liq- uid makes an angle of a = 30 with respect to the vertical. air water flashlight ray w a At what angle (with respect to the vertical) is the flashlight being held under transparent liquid? Correct answer: 23 . 5782 . Explanation: By Snells Law n a sin a = n w sin w , where n a and n w are the indices of refraction for each substance and a and w are the inci- dent angles to the boundary in each medium, respectively. Assume that the surface of the transparent liquid is a level horizontal plane, thus each angle with respect to the vertical represents the incident angle in each medium. The index of refraction of air is (nearly) n a = 1 . 0 while the index of refraction of trans- parent liquid is given as n w = 1 . 25. The inci- dent angle in the air is given to be a = 30 . Hence sin w sin a = n a n w sin w sin 30 = 1 1 . 25 sin w = . 5 1 . 25 w = arcsin(0 . 4) w = 23 . 5782 . 002 (part 2 of 2) 10.0 points The flashlight is slowly turned away from the vertical direction. At what angle will the beam no longer be visible above the surface of the pool? Correct answer: 53 . 1301 . Explanation: This is solved in the same fashion as Part 1. When the light ceases to be visible outside the transparent liquid, then a 90 . The sin 90 = 1. Hence (from above), sin w = n a n w w = arcsin parenleftbigg 1 1 . 25 parenrightbigg w = 53 . 1301 . 003 10.0 points A flashlight on the bottom of a 3.86 m deep swimming pool sends a ray upward and at an angle so that the ray strikes the surface of the water 2.81 m from the point directly above the flashlight....
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This note was uploaded on 01/21/2010 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
- Spring '08