978_Physics ProblemsTechnical Physics

978_Physics ProblemsTechnical Physics - Chapter 35 Q35.24...

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Unformatted text preview: Chapter 35 Q35.24 319 A mirage occurs when light changes direction as it moves between batches of air having different indices of refraction because they have different densities at different temperatures. When the sun makes a blacktop road hot, an apparent wet spot is bright due to refraction of light from the bright sky. The light, originally headed a little below the horizontal, always bends up as it first enters and then leaves sequentially hotter, lower-density, lower-index layers of air closer to the road surface. SOLUTIONS TO PROBLEMS Section 35.1 The Nature of Light Section 35.2 Measurements of the Speed of Light P35.1 The Moon’s radius is 1.74 × 10 6 m and the Earth’s radius is 6.37 × 10 6 m . The total distance traveled by the light is: e j d = 2 3.84 × 10 8 m − 1.74 × 10 6 m − 6.37 × 10 6 m = 7.52 × 10 8 m . 7.52 × 10 8 m = 2.995 × 10 8 m s = 299.5 Mm s . 2.51 s This takes 2.51 s, so v = e jb g 8 ∆x 2 1.50 × 10 km 1 000 m km c= = = 2. 27 × 10 8 m s = 227 Mm s t 22.0 min 60.0 s min P35.2 ∆x = ct ; P35.3 The experiment is most convincing if the wheel turns fast enough to pass outgoing light through 2 one notch and returning light through the next: t = c F2 I θ = ω t = ωG J HcK a fb g e jaf j 2.998 × 10 8 2π 720 cθ ω= = = 114 rad s . 2 2 11. 45 × 10 3 so e The returning light would be blocked by a tooth at one-half the angular speed, giving another data point. P35.4 (a) For the light beam to make it through both slots, the time for the light to travel the distance d must equal the time for the disk to rotate through the angle θ, if c is the speed of light, dθ dω = , so c = . cω θ (b) We are given that d = 2.50 m , θ = c= dω θ FG H IJ K FG H IJ K 2π rad 1.00° π rad = 2.91 × 10 −4 rad , ω = 5 555 rev s = 3.49 × 10 4 rad s 60.0 180° 1.00 rev a2.50 mfe3.49 × 10 = 2.91 × 10 −4 4 rad s rad j = 3.00 × 10 8 m s = 300 Mm s ...
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