Notes

Diffraction grating Diffraction grating is an extremely useful device. In one of its form it consists of a very large number of narrow slits side by side. The slits are separated by opaque spaces. Diffraction gratings are of two types; transmission grating and reflection grating. Transmission grating: When a wavefront is incident on a grating … Read more

Diffraction phenomena can conveniently divided into two groups. Fresnel Diffraction Phenomena: In the Fresnel class of diffraction, the source or the screen or the both are at finite distances from the aperture or obstacle causing diffraction. In this case, the effect at a specific point on the screen due to the exposed incident wavefront is considered … Read more

Diffraction The rhythmic variations in intensity and the bending of light around the corners of an obstacle or the encroachment of light into the region of geometrical shadow constitute a class of phenomena known as the diffraction of light.

Newton’s rings and its formation :  When a Plano-convex lens of long focal length is placed on a plane glass plate, a thin film of air is enclosed between the lower surface of the lens and the upper surface of the plate. The thickness of the air film is very small at the point of … Read more

Fringe width  The distance between any two consecutive bright or dark fringe is known as fringe width. Symbolically the fringe width is β and

Two independent sources of light can not produce interference because a large number of difficulties are involved. The two sources may emit light waves of largely different amplitude and wave length and the phase difference between the two may change with time. That’s why interference of light is produced by two coherent sources which are … Read more

Coherent sources Two sources are said to be coherent if they emit light waves of same frequency, nearly equal amplitude and are always in phase with each other. Realization in practice In practice it is not possible to have two independent sources which are coherent. But for experimental purpose, two virtual sources formed by a … Read more

Interference of light:  Wave emitted from two coherent sources having the same wavelength, equal or nearly equal amplitude when passes through a point in a medium, then superposition takes place.  During superposition, if the two waves reaching the point in the same phase then the intensity will be maximum that is bright. But if the … Read more

Huygens principle To explain the propagation of light through ether, Huygens proposed the following principles for the construction of a wavefront at a subsequent time from the known position of the wavefront at any given instance. Every point on a primary wavefront may be considered as the secondary source of disturbance. Secondary waves or wavelets … Read more