Homework 6 solutions

Homework 6 solutions - WebAssign Problems 1. In an...

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WebAssign Problems 1. In an experiment to measure the speed of light using the apparatus of Fizeau (see Fig. 35.2), the distance between light source and mirror was 11.45 km and the wheel had 720 notches. The experimentally determined value of c was 2.998 × 10 8 m/s. Calculate the minimum angular speed of the wheel for this experiment. Solution: The experiment is most convincing if the wheel turns fast enough to pass outgoing light through one notch and returning light through the next: 2 t c = l 2 t c θ ω = = l so ( ) ( ) ( ) 8 3 2.998 10 2 720 114 rad s 2 2 11.45 10 c π × = = = × l . The returning light would be blocked by a tooth at one-half the angular speed, giving another data point. 2. The two mirrors illustrated in Figure below meet at a right angle. The beam of light in the vertical plane P strikes mirror 1 as shown. (a) Determine the distance the reflected light beam travels before striking mirror 2. (b) In what direction does the light beam travel after being reflected from mirror 2? Solution:
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From geometry, 1.25 m sin40.0 d = ° so 1.94 m d = . (b) 50.0 above the horizontal ° or parallel to the incident ray. Mirror 2 50° 40° 50° 50° 40° d i 1 = 40° i 2 = 50° Mirror 1 1.25 m 40.0° 1.25 m Mirror 1 Mirror 2 Light beam P 3. The wavelength of red helium–neon laser light in air is 632.8 nm. (a) What is its frequency? (b) What is its wavelength in glass that has an index of refraction of 1.50? (c) What is its speed in the glass? Solution: (a) 8 14 7 3.00 10 m s 4.74 10 H z 6.328 10 m c f λ - × = = = × × (b) air glass 632.8 nm 422 nm 1.50 n = = = (c) 8 8 air glass 3.00 10 m s 2.00 10 m s 200 M m s 1.50 c v n × = = = × = 4. A ray of light is incident on a flat surface of a block of crown glass that is surrounded by water. The angle of refraction is 19.6°. Find the angle of reflection. Solution: We find the angle of incidence: 1 1 2 2 1 1 sin sin 1.333sin 1.52sin19.6 22.5 n n θ = = ° = ° d. Taking n = 1.50, find the value of d.
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This note was uploaded on 11/22/2010 for the course PHYSICS Physics 7C taught by Professor Ilyakrivorotov during the Winter '10 term at UC Irvine.

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Homework 6 solutions - WebAssign Problems 1. In an...

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