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Unformatted text preview: PHYS408 Fall 2008 Mastering Physics Assignment #6 Solutions Problem 20.12 The displacement of a wave traveling in the positive xdirection is D ( x, t ) = ( 3.5 (cm) ) sin ( 2.7x124t ), where x is in m and t is in s. (a) What is the frequency of this wave? = 2 f = 124 / s f = 2 = 124 / s 2 = 19.7/ s = 19.7 Hz (b) What is the wavelength of this wave? k = 2 = 2.7/ m = 2 k = 2 2.7/ m = 2.33 m (c) What is the speed of this wave? v = f = 2.33 m ( ) 19.7 Hz ( ) = 45.9 m / s Problem 20.16 (a) A spherical wave with a wavelength of 2.0 m is emitted from the origin. At one instant of time, the phase at r = 4.0 m is pi (rad). At that instant, what is the phase at r =3.5 m? Since time is constant, we can simply ask what is the change in phase: = k x k = 2 = 2 2.0 m = / m x = 3.5 m 4.0 m ( ) = 0.5 m = / m 0.5 m ( ) = 0.5 = f x = 3.5 m ( ) i x = 4.0 m ( ) Where I have labeled the x values to make the initial and final clear. f = i + = 0.5 = 0.5 = 2 (b) What is the phase at r =4.5 m at the same instant? x = 4.5 m 4.0 m ( ) = 0.5 m = / m 0.5 m ( ) = 0.5 f = i + = + 0.5 = 1.5 = 3 2 Problem 20.20 (a) What is the wavelength of a 2.0 MHz ultrasound wave traveling throughWhat is the wavelength of a 2....
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 Spring '08
 BEANE
 Physics, Light, Frequency, Hertz

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