Interference of light and classification of Interference

Interference of light:

When two or more waves, having the same frequency and constant phase difference, travel simultaneously in the same region of a medium, these waves superimpose on each other and a resultant wave is obtained which has intensity at some points maximum and some points minimum in the region. This is phenomenon is known as interference of light.

When the intensity of the resultant wave is maximum in the region then this is called constructive interference.

when the intensity of the resultant wave is minimum in the region then this is called destructive interference.


Classification of Interference:

The phenomenon of interference may be grouped into two categories depending upon the formation of two coherent sources in practice.The interference of light is classified into two categories:

  • Division of amplitude

  • Division of wavefront


    • Division of amplitude:

    In this method, the amplitude of the incident beam is divided into two or more parts are either by partial reflection or refraction. the beams travel in different paths, are superimposed on each other, and form the interference pattern.

    Example: Interference in the thin film, Newton's rings, and Michelson's interferometer are examples of two-beam interference and Fabry-Perot interferometer is the example of multiple-beam interference.


    Division of Wavefront:

    Under this category, the coherent sources are obtained by dividing the wavefront, originating from a common source, by employing mirrors, biprisms, or lenses. This class of interference requires initially a point source or a narrow slit source. The instruments used to obtain coherent sources and hence interference by division of wavefront are fresnel biprism fresnel Mila mirror Lloyd's mirror laser etc.