1. In a single-slit diffraction pattern on a flat screen, the central bright fri

Question

1. In a single-slit diffraction pattern on a flat screen, the central bright fringe is 1.3 cm wide when the slit width is 4.0 x 10-5 m. When the slit is replaced by a second slit, the wavelength of the light and the distance to the screen remaining unchanged, the central bright fringe broadens to a width of 1.7 cm. What is the width of the second slit? It may be assumed that is so small that sin is approximately equal to tan .

2.A diffraction grating has 2593 lines per centimeter, and it produces a principal maximum at = 28.2°. The grating is used with light that contains all wavelengths between 410 and 660 nm. What are the two wavelengths of the incident light that could have produced this maximum? Give the longer wavelength as answer (a).

A)?
B)?

Explanation / Answer

d = 1/2593 cm, = 28.2°, wavelengths [410, 660] nm. Find two wavelengths.

dsin = m

= 1822/m nm

m = 1, = 1822 > 660 nm

m = 2, = 911 > 660 nm

m = 3, = 607 nm = 6.07*10-7 m (answer A)

m = 4, = 450 nm = 4.50*10-7 m (answer B)

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