Newton's ring belongs to thin-film interference, that is, a plano-convex lens with a large radius of curvature is superimposed on the flat glass and reflected on the lower surface of the convex lens and the flat glass (the film is an air film) to form interference, instead of reflecting on the upper and lower surfaces of the convex lens to form interference. The air film thickness on the lower surface of convex lens and flat glass is uneven, the optical path difference is uneven, and the distance from the center of the circle is uneven, so the gap is unequal.
Newton ring, also known as Newton ring. In optics, Newton's ring is a thin film interference phenomenon. The interference pattern of light is a series of concentric rings alternating with light and dark. For example, the convex surface of a convex lens with a larger radius of curvature is in contact with flat glass, and the contact point can be regarded as a dark spot surrounded by some bright and dark colored rings; When illuminated with monochromatic light, it appears as some monochromatic circles with alternating light and dark. The distances between these circles are unequal, and gradually narrow with the increase of the distance from the center point. They are interference fringes formed by the mutual interference of light reflected from a sphere and a plane.