In order to verify the wave nature of light and to measure the wavelength of light or to observe interference of light, Michelson invented his famous interferometer in which he divide the light from single source into two parts with the help of semi silvered glass plate.
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The Michelson interferometer was invented by an American physicist A.A.Michelson (1852-1931). The Michelson interferometer played an interesting role in the history of science during the latter part of the nineteenth century. It has a great scientific importance and had an equally important role in establishing high precision standards of the unit of length. In contrast to the Young's double slit experiment for producing interference fringes which make use of light from two narrow sources, the Michelson interferometer uses light from broad, spread source (extended source).
The essential features of a Michelson interferometer are shown schematically in figure given below:
The essential features of a Michelson interferometer are shown schematically in figure given below:
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| Fig Schematic diagram of Michelson Interferometer |
Michelson interferometer consists of two highly polished plane mirrors M1 and M2. The mirror M1 is fixed where as the mirror M2 is moveable as shown in the above figure. In addition to this, it has glass plate C which has a thin coating of silver on its right side. This partially silvered plate is called beam splitter and is inclined at 45° relative to the incident light beam. It has also another plate D which is identical to the plate C except it is not silvered. Its purpose is to ensure that the beam I and II pass through the same thickness of glass. Therefore it is known as compensating plate. This is particularly important when white light fringes (colored fringes) are desired.