Newton’s Rings

This apparatus illustrates an interference pattern of light waves. The top surface is a plano-convex lens while the bottom is a flat glass surface. The air film between the glass surfaces varies in thickness from zero at the point of contact to some larger value t at points distant from the contact point. The radius of curvature of the lens is large compared with the radius of the hole in the frame holding the glass pieces. Viewing the system from above will show a pattern of light and dark rings. This interference pattern is called Newton’s rings after their discoverer.