In this Physics video lecture for B.Sc. we explained the reason of using compensating plate in Michelson Interferometer. Without the use of the compensating plate, also known as compensation plate, light waves of different wavelength would create different patterns and hence the fringes would not be sharp enough. In the last video we discussed on its applications or usages. It is based on the principle of interference due to path difference of two coherent sources. It is very popular due to its simple design.
It is used :
1) To determine wavelength of monochromatic light
2) To find the difference in wavelength between two neighbouring spectral lines
3) To find the refractive index and thickness of a thin transparent material
4) To measure the standard metre in terms of wavelength of light
5) To find the refractive index of a gas
When the knob of the interferometer is rotated one of the mirrors move and hence path difference is created. Due to the path difference interference fringes cross the centre of the interference field on the screen. Counting the crossing of the fringes and the amount the mirror is shifted, we can determine the wavelength of the monochromatic light from the source.
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