NV6104 Newton' s ring apparatus is one of the basic experiment at graduation level. With the help of this apparatus, the wave nature of light is confirmed. It is based on the phenomenon of interference of light waves obtained from single coherent (of same frequency and constant or zero phase difference). The phenomenon of Newton's ring, is the result of interference between the partially reflected and partially transmitted rays from both the lower curved surface of plano-convex lens as well as upper surfaces of the glass plate. When viewed with a monochromatic light, it appears as a series of concentric, alternating bright and dark rings centered at the point of contact between the two surfaces. The thickness of the film is radially symmetrical and increases outwards from the point of contact. By studying the ring pattern, we can determine the wavelength of the monochromatic light and also the refractive index of a given transparent liquid medium present in the wedge - shaped film.