Fall 2011 Homework 28 Solutions

Fall 2011 Homework 28 Solutions - Physics 21 Fall, 2011...

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Unformatted text preview: Physics 21 Fall, 2011 Solution to HW-28 33-31 Unpolarized light of intensity 26.0 W/cm 2 is inci- dent on two polarizing filters. The axis of the first filter is at an angle of 24.8 counterclockwise from the vertical (viewed in the direction the light is traveling) and the axis of the second filter is at 65.0 counterclockwise from the vertical. What is the intensity of the light after it has passed through the second polarizer? When the unpolarized light (intensity I ) passes through the first polarizer, its intensity decreases by half and it will be polarized in the same direction as the axis of the first po- larizer. Therefore the intensity after the first polarizer is I 1 = I /2 = 13 W/cm 2 . The light is now polarized, so when it passes through the second polarizer its intensity decreases by another factor of cos 2 , according to Malus Law: I 2 = I 1 cos 2 ( ) , where I 2 is the intensity after the second polarizer, and is the angle between the polarization of the light and the axis of the polarizer. Since the axis of the first polarizer is at 24.8 , and the axis of the second polarizer is at 65.0 in the same direction, the angle between them is the difference, or 40.2 . Then I 2 = (13 W / cm 2 ) cos 2 (40 . 2 ) = 7 . 58 W / cm 2 . 34-58 Saturn is viewed through the Lick Observatory re- fracting telescope (objective focal length 18 m). If the di- ameter of the image of Saturn produced by the objective is 1 . 7 mm, what angle does Saturn subtend from when viewed from earth? In the figure above (taken from page 1193 in the textbook), it is shown that a refracting telescope is made of two lenses, the objective and the eyepiece. Note that in this problem, we are only dealing with the objective lens. Saturns average distance from the earth is 1 . 433 10 12 m, which is very large compared to the other distances in this problem, so we can...
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This note was uploaded on 12/18/2011 for the course PHYS 021 taught by Professor Hickman during the Spring '08 term at Lehigh University .

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Fall 2011 Homework 28 Solutions - Physics 21 Fall, 2011...

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