# _010 - Solution for Practice Test 11 for Test 4 Solution to...

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Unformatted text preview: Solution for Practice Test 11 for Test 4 Solution to Practice Test Problem 11.1(Time for Light to Reach Pluto) Problem: Pluto is 1 . 4 billion miles = 2 . 24 × 10 12 m from the Earth. How long does it take a radio signal to reach Pluto from the Earth? Select One of the Following: (a) 2 . 2s . (b) 2200s . (c-Answer) 7500s . (d) 75s . (e) Toby Solution (c): time = distance speed = 1 . 4 × 10 9 miles 1 . 86 × 10 5 miles s ≈ 7500s Total Points for Problem: 2 Points Solution to Practice Test Problem 11.2(Focal Length of Plano-Convex Lens) Problem: A plano-convex lens is formed of one plane surface and one convex surface. The convex surface has radius | 75cm | . The lens is formed of a material with index of refraction 1 . 6 . What is the focal length of the lens? Select One of the Following: (a-Answer) 125cm . (b) 37 . 5cm . (c)- 125cm . (d)- 37 . 5cm . (e) Toby. Solution (a): 1 f = ( n- 1) parenleftbigg 1 r 1- 1 r 2 parenrightbigg = (1 . 6- 1) parenleftbigg 1 75cm- 1 ∞ parenrightbigg f = 125cm Total Points for Problem: 2 Points Solution to Practice Test Problem 11.3(Intensity of Light Passing into Diamond) Problem: Sunlight with intensity of 1000 W m 2 shines at normal incidence on a diamond (index of refraction 2 . 4 ). What is the intensity of the light that passes into the diamond? 1 Select One of the Following: (a) 412 W m 2 . (b) 170 W m 2 . (c-Answer) 830 W m 2 . (d) 588 W m 2 . (e) Toby Solution (c): The reflected intensity is: I r = parenleftbigg n i- n t n i + n t parenrightbigg 2 I i = parenleftbigg 1- 2 . 4 1 + 2 . 4 parenrightbigg 2 parenleftbigg 1000 W m 2 parenrightbigg I r = 170 W m 2 Energy is conserved, so I t = I i- I r = 830 W m 2 Total Points for Problem: 2 Points Solution to Practice Test Problem 11.4(Minimum Angle for Wave Guide Propagation) Problem: For a wave guide to work, the light travelling through it must undergo total internal reflection. If the index of refraction of the optical fiber forming the wave guide is 1 . 9 , what is the minimum angle the light in the fiber can make with the normal of the side of the fiber for the light to travel down the fiber? Select One of the Following: (a) 15 . 46 ◦ . (b) . 526 ◦ . (c-Answer) 31 . 76 ◦ . (d) . 009 ◦ . (e) Toby. Solution (c): n i sin θ i = n t sin θ t where θ t = 90 ◦ θ i,min = arcsin parenleftbigg n t n i parenrightbigg = arcsin parenleftbigg 1 1 . 9 parenrightbigg = 31 . 76 ◦ Total Points for Problem: 2 Points 2 Solution to Practice Test Problem 11.5(Clinton Library Mirror) Problem: To look high tech, the Clinton library in Little Rock uses a polished stainless steel plaza with a glass statue in the center of the plaza. Because the contract for the statue and plaza goes to the lowest bidder, the plaza sags producing a mirror with radius of curvature 100ft . How high must the statue be above the plaza to be at the focal point of the mirror formed by the plaza and thus explode if the dedication is on the first sunny...
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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.

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_010 - Solution for Practice Test 11 for Test 4 Solution to...

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