Engineering applications of Interference phenomenon :

While discussing various methods of producing interference fringes, we discussed how these can be used to determine the wavelength of monochromatic light, the separation between the two closely spaced wavelengths, thickness and refractive index of thin transparent sheet and refractive index of a liquid.

Apart from these, interference phenomenon finds many interesting engineering applications. These include testing of flatness of optical surfaces, the angle of beam splitter, testing of prism and lens for chromatic aberrations,, measurement of thickness of a thin film, collimation testing, measurement of angle of a wedge etc. We shall discuss a few in the following.

Testing of optical surfaces –

The optical surfaces are tested either by contact method where the test surface is put in contact with the master surface (an experimental arrangement similar to Newton's ring method) or by inserting the test surface in the path of two beams (experimental arrangement is similar to Michelson interferometer) and is known as Twyman-Green interferometer)