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Introductory Physics Volume Two

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7.11 Homework 155<br />

Second Min<br />

First Min<br />

Source<br />

θ<br />

Central Max<br />

Fact: Single Slit Diffraction<br />

If light is passed through a single slit of width a, then the angle<br />

between the central maximum and the first minimum is given by<br />

a sin θ = λ<br />

§ 7.11 Homework<br />

⊲ Problem 7.12<br />

A pair of speakers is configured as shown, with a microphone placed directly<br />

in front of one of the speakers. Sound waves having a wavelength<br />

10 cm are coming from the speakers. The speakers are in phase with<br />

each other. What is the minimum distance d between the speakers so<br />

that no sound is heard at the microphone labeled P ?<br />

1 m<br />

P<br />

d<br />

⊲ Problem 7.13<br />

A material having an index of refraction of 1.30 is used to coat a piece<br />

of glass (n = 1.50). What should be the minimum thickness of this film<br />

to minimize reflection of 500nm light?<br />

⊲ Problem 7.14<br />

A soap bubble of index of refraction 1.33 strongly reflects both the red<br />

and the green components of white light. What film thickness allows<br />

this to happen? (In air, λ red = 700nm, λ green = 500nm.)

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