Diffraction in Wave Optics Overview

The phenomenon of bending of the light and the obstacle is called diffraction. It is exhibited by not only the light waves but also by sound waves, Matter waves and water waves. Because of the diffraction effect of sound waves, we are able to hear the sounds made by the other people that are there in a different room. It is just because sound bends at the Windows.

The encroachment of the light into the darker regions is expressed as diffraction. If an obstacle is placed in the path of the light, the entire corresponding region is supposed to become dark. But because of the encroachment of the light, even the supposed to be darker region consists of bright and dark bands. The formation of the bright and dark bands is due to mixing of the waves that are coming from the same source that are split up into multiple sources.

The diffraction pattern consists of alternate bright and dark bands. But the intensity of All bright bands as not equal. The bright bandit the Centre has maximum brightness and it is called principal maximum. The dark bands surrounding the bright band are called as minima.

The other bright bands have decreasing intensity away from the principal axis and they are called secondary maxima.

As the bands progresses, bright bands becomes less bright and the dark bands becomes less dark. It means after a few bands will become difficult to identify that who is a bright band and who is the dark.

We can derive a small mathematical equation for minimum and maximum in a diffraction patron as shown below. Here we have only one source and when it is restricted by the obstacle it behaves like multiple sources. The resultant intensity is being observed on your screen. We can write equation for the bright and dark spots as shown below.