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Homework 21 Solutions

# Homework 21 Solutions - lim(kl9356 Homework 21...

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lim (kl9356) – Homework 21 – Weathers – (22202) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 3) 10.0 points The wavelength of red light in air is 957 nm . What is its frequency? The speed of light in air is 2 . 99792 × 10 8 m / s. Correct answer: 3 . 13263 × 10 14 Hz. Explanation: Let : c = 2 . 99792 × 10 8 m / s , and λ = 957 nm = 9 . 57 × 10 7 m . c = f λ f = c λ = 2 . 99792 × 10 8 m / s 9 . 57 × 10 7 m = 3 . 13263 × 10 14 Hz . 002 (part 2 of 3) 10.0 points What is its wavelength in glass that has an index of refraction of 1 . 12? Correct answer: 854 . 464 nm. Explanation: Let : n = 1 . 12 . From Snell’s law, while travel in glass, speed of light is decreased by a factor of refraction index n ; so the wavelength is also decreased due to the larger refraction index of glass λ glass = λ air n = 957 nm 1 . 12 = 854 . 464 nm . 003 (part 3 of 3) 10.0 points What is its speed in the glass? Correct answer: 2 . 67672 × 10 8 m / s. Explanation: From Snell’s law, light speed in glass is v = c n = 2 . 99792 × 10 8 m / s 1 . 12 = 2 . 67672 × 10 8 m / s . 004 (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 . 27. 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 θ a = 26 with respect to the vertical. θ θ air water flashlight ray w a At what angle (with respect to the vertical) is the flashlight being held under transparent liquid? Correct answer: 20 . 1924 . Explanation: By Snell’s Law n a sin θ a = n w sin θ w , where n a and n w are the indices of refraction for each substance and θ a and θ 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 . 27. The inci- dent angle in the air is given to be θ a = 26 .

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Homework 21 Solutions - lim(kl9356 Homework 21...

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