homework4

# homework4 - Homework Set 4 Due Wednesday 07/20 Problem 1 A...

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Homework Set 4 Due Wednesday, 07/20 Problem 1: A room has two open windows on the same wall, at a distance of 4 meters apart. A loud car horn is sounded outside. An observer along the opposite wall, 15 meters away, can hear the sound loudly when he is directly opposite the point between the two windows, but if he moves to the point directly across from one of the windows, the sound becomes much quieter, growing louder again as the observer moves farther away from the center. What is the main frequency of the car horn? Problem 2: Laser light of wavelength l = 520 nm is incident on a CD at an angle of 30 degrees to the normal, as shown in the diagram. The reflected light is projected onto a screen. The diffraction fringes are found to lie in directions 1.2 degrees apart. What is the separation between the tracks on the CD? Hint: the laser light arriving at the different tracks already has a path length difference from the laser, in addition to the path length difference to the screen.

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Problem 3: In the year 2265, United Earth spaceships are equipped with 100GW laser cannons, firing infra-red laser beams with a wavelength of 1.0 μ m . The laser beams have a diameter of 25 cm when they emerge from the laser cannon. Aliens from Alpha Centauri are invading. The alien spaceships have shields that can withstand infra-red light intensities of up to 1GW / m 2 . What is the effective range of the laser cannons against the alien spaceships? Problem 4: A thin film with thickness d = 400 nm has an index of refraction n = 1.42. Light is incident on the film at an angle of 30 degrees with respect to the normal.
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## This note was uploaded on 09/19/2011 for the course PHYS 1C taught by Professor Smith during the Spring '07 term at UCSD.

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homework4 - Homework Set 4 Due Wednesday 07/20 Problem 1 A...

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