In a Newton's ring set up, the two super imposing light waves are produced by division of amplitude. The set up consists of a plano convex lens placed on a flat (plane) glass surface as shown in figure. The light from a broad monochromatic source is made to fall on a glass plate inclined at 45 . The reflected rays are incident on plano convex lens and are reflected from the top and bottom surface of air film formed between the convex surface and flat surface of lens and glass plate respectively and interference pattern (circular rings) is observed on the screen (eyepiece) with their center at O '