1 A light wave has a 670 nm wavelength in air Its wavelength

1.

A light wave has a 670 nm wavelength in air. Its wavelength in a transparent solid is 376 nm.

(a) What is the speed of light in this solid?

2.

In a single-slit experiment, the slit width is 215 times the wavelength of the light. What is the width of the central maximum on a screen 2.2 m behind the slit?

3.

You need to use your cell phone, which broadcasts an 840 MHz signal, but you\'re behind two massive, radio-wave-absorbing buildings that have only a 15 m space between them. What is the angular width of the electromagnetic wave after it emerges from between the buildings?

4.

You want to photograph a circular diffraction pattern whose central maximum has a diameter of 1.2 cm. You have a helium-neon laser ( = 633 nm) and a 0.12 mm diameter pinhole. How far behind the pinhole should you place the viewing screen?

Solution

2) Single slit diffraction a = 215 * W L

a * sin theta = W L

sin theta = W L / a

2 * 2.2 * tan theta = 2 * 2.2 * sin theta = 4.4 * W L / a

= 4.4 / 215

= 2.05 cm

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3) theta = sin^-1(W L / a)

= sin^-1 (3 * 10⁸/ (8.4 * 10⁸ * 15) )

= 1.36 deg

The angular width is twice = 2 * 1.36 = 2.72 deg