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Unformatted text preview: Physics 6C HW#2 solution April 17, 2008 25.30 a) The index of refraction is n = c v . From this relation, we can write Snell’s law in terms of velocities. sin θ 2 sin θ 1 = v 2 v 1 θ 2 = 90 ◦ at critical angle. sin(90 ◦ ) sin θ c = 1850 m/s 343 m/s θ c = sin 1 (0 . 185) = 10 . 7 ◦ b) Sound can be totally reflected if it is traveling in the medium where it travels slower. air . c) Sound in air falling on the wall from the most di rection is totally reflected. Thus, the wall is a good mirror. 1 25.53 a) For polystyrene surrounded by air, the critical angle θ 3 is, θ 3 = sin 1 ( 1 . 00 1 . 49 ) = 42 . 2 ◦ From geometry, θ 2 = 90 ◦ θ 3 = 47 . 8 ◦ θ 3 is the minimum angle of total internal reflection when it is the critical angle. Since θ 2 = 90 ◦ θ 3 , θ 2 becomes the maximum when the θ 3 is the minimum and θ 1 is the maximum as well. The maximum θ 1 can be found from Snell’s law....
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This note was uploaded on 07/02/2008 for the course PHYS 6C taught by Professor Staff during the Spring '01 term at UCLA.
 Spring '01
 staff
 Physics, Thermodynamics, Light

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