Principle of Michleson Interferometer

The Michleson Interferometer is a two interferometer, when two coherent light beams interface with each other than maxima (bright fringe) occur where maxima of one beam superimpose with maxima of other beam and minima (dark fringe) occur where maxima of one beam superimpose with minima of other beam. For good quality of fringes we need coherent source so we use a beam splitter for split a beam into two parts. Beam travel at 90 degree with each other. Now use two mirrors for reflect back beams to beam splitter and superimpose with each other.

A good quality michleson interferometer can be used for measurement operations like:-

1. Wavelength of light 
2. Refractive index of glass slits 
3. Refractive index of air or gas

Now the same principle used for detection of change in gravitational waves as discus in various posts.