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Unformatted text preview: Solution for Practice Test 12 for Test 4 Solution to Practice Test Problem 12.1(Nicks Critical Angle Problem) Problem: Just because Nick insisted, what is the index of refraction of a material where the critical angle is 42 in air? Select One of the Following: (a) 1 . 55 (b) 1 . 67 (c) . 68 (dAnswer) 1 . 49 (e) Toby Solution By Snells law, n i sin 42 = n t sin 90 = 1 , where n i is what were trying to find and n t = 1 . So n i = 1 / sin 42 = 1 . 49 . Total Points for Problem: 3 Points Solution to Practice Test Problem 12.2(Sunlight on Solar Sail) Problem: Sunlight has intensity of 1300W / m 2 in space near the earth. The Planetary Society is launching a light sail with total area . 6 10 3 m 2 . Calculate the total force at normal incidence on the sail if it is perfectly reflecting. Remember to multiply the force by two for perfect reflection. Select One of the Following: (a) 1 . 2 10 6 N (b) 17 . 2 10 3 N (c) 7 . 8 10 3 N (dAnswer) 5 . 2 10 3 N (e) Toby. Solution The radiation pressure on the sail is P r = 2 I c where the two comes from the perfectly reflecting condition. The force is then F = P r A = 2 A I c = 2(0 . 6 10 3 m 2 ) 1300W / m 2 3 10 8 m s = 5 . 2 10 3 N where A is the area. Total Points for Problem: 3 Points 1 Solution to Practice Test Problem 12.3(Which One is Faraday?) Problem: The third Maxwell equation is contintegraldisplay C vector E d vector l = d dt integraldisplay S vector B ndA What is the name of this equation? Select One of the Following: (a) Gauss Law. (b) No Magnetic Monopoles (c) Amperes Law (dAnswer) Faradays Law (e) Tobys Law Solution Faradays Law Total Points for Problem: 3 Points Solution to Practice Test Problem 12.4(Time to Earth) Problem: The radius of the earths orbit around the sun is 1 . 5 10 11 m . How long does it take the suns light to reach the Earth, neglecting the radius of the sun. Select One of the Following: (a) About an hour. (bAnswer) About 10 minutes. (c) About a minute. (d) No time. (e) Toby Solution t = distance speed = 1 . 50 10 11 m 3 10 8 m s = 500 s = 8 1 3 minutes Total Points for Problem: 3 Points Solution to Practice Test Problem 12.5(Light Striking Flint Glass) Problem: A laser is shone on the side of a Flint glass rectangle with index of refraction 1 . 66 , making an angle of 45 to the surface of the square, as shown below. The first surface that the light intersects is surface 1 . The surface the refracted beam hits first is surface 2 . Does any light escape surface 2 ? 2 Select One of the Following: (a) Yes, light escapes. (bAnswer) No, no light escapes. (e) Toby. surface 1 surface 2 Flint Glass Solution surface 1 surface 2 Flint Glass total internal reflection r i i 2 refracted Definitions refracted Angle of refraction at first surface i Angle of Incidence c Critical Angle i 2 Angle of Incidence for second surface The angle of refraction is found from Snells law,...
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This note was uploaded on 05/04/2008 for the course PHYS 2074 taught by Professor Stewart during the Spring '08 term at Arkansas.
 Spring '08
 Stewart
 Physics

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