Chapter 19.1, Problem 10SSC

To determine

To Describe: The way, the wave behaves when it encounters the slits and the reason for the observed pattern of bright and dark bands.

Explanation of Solution

Introduction:

The diffraction of light waves is an optical phenomenon defined as the bending of light waves around the edges of an obstacle and illuminates the region where the geometrical shadow of the obstacle is expected. The interference of light waves is the superposition of two light waves to produce a resultant wave with larger, lower or an identical amplitude. The interference may be constructive or destructive. If the two light waves superpose in such a way that the crest of one wave falls on the crest of the second wave and the trough of one wave falls on the trough of the second wave, then the amplitude of the resulting wave is larger and is called constructive interference. If the two light waves superpose in such a way that the crest of one wave falls on the trough of the second wave, then the amplitude of the resulting wave is zero and is called destructive interference.

It is given that two very narrow slits in cardboard are illuminated by a monochromatic red light and a pattern of bright and dark bands is seen on the white paper that is placed far from the slits. This can be described as - when the light wave encounters the slits, the wave bends and there will be diffraction of light waves from the slits. Interference takes place between the light waves that are diffracted from the two slits. The diffraction pattern can be seen by placing the screen far from the slits. The interference between the light waves diffracted from the two slits may be constructive or destructive. For constructive interference, the band produced in the pattern is bright and for destructive interference, the dark region is formed in the pattern.