various systems based on these fundamentals are usually created because they are familiar to notice these phenomenon. These types of systems find a number of applications in science and engineering such as measurement of wavelength of a light source, the wavelength difference between two closely separated waves, the optical flatness of surfaces, thickness of the film, refractive index of material etc. We shall be discussing some of these systems and their applications in the following sections. The major systems for observing interference phenomenon are as follows