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Ch33Word - Ch 33 p 1 CHAPTER 33 Light Reflection and...

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Ch. 33 p. 1 CHAPTER 33 – Light: Reflection and Refraction 1. ( a ) The speed in ethyl alcohol is v = c / n = (3.00 × 10 8 m/s)/(1.36) = 2.21 × 10 8 m/s . ( b ) The speed in lucite is v = c / n = (3.00 × 10 8 m/s)/(1.51) = 1.99 × 10 8 m/s . 2. We find the index of refraction from v = c / n ; 2.29 × 10 8 m/s = (3.00 × 10 8 m/s)/ n , which gives n = 1.31 . 3. The time for light to travel from the Sun to the Earth is ? t = L / c = (1.50 × 10 11 m)/(3.00 × 10 8 m/s) = 5.00 × 10 2 s = 8.33 min . 4. We convert the units: d = (4.2 ly)(3.00 × 10 8 m/s)(3.16 × 10 7 s/yr) = 4.0 × 10 16 m . 5. The length in space of a burst is ? s = c ? t = (3.00 × 10 8 m/s)(10 –8 s) = 3 m . 6. The speed in water is v water = c / n water . We find the index of refraction in the substance from v = c / n ; 0.92 v water = 0.92 c / n water = c / n , which gives n = 1.33/0.92 = 1.45 . 7. The eight-sided mirror would have to rotate 1/8 of a revolution for the succeeding mirror to be in position to reflect the light in the proper direction. During this time the light must travel to the opposite mirror and back. Thus the angular speed required is ω = ? θ /? t = (2p rad/8)/(2 L / c ) = (p rad) c /8 L = (p rad)(3.00 × 10 8 m/s)/8(35 × 10 3 m) = 3.4 × 10 3 rad/s (3.2 × 10 4 rev/min). 8. For a flat mirror the image is as far behind the mirror as the object is in front, so the distance from object to image is d o + d i = 1.8 m + 1.8 m = 3.6 m . 9. We show some of the rays from the tip of the arrow that form the three images. Single reflections form the two side images. Double reflections form the third image. The two reflections have reversed the orientation of the image. I 1 I 2 I 3 Object
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