Not Newton’s rings
Stories from Physics for 11-14 14-16
Newton’s rings are a well-known interference phenomenon that occurs when an observer looks vertically down through a plano-convex lens of large focal length, placed curved side down, on a glass plate. Dark rings appear because rays of monochromatic light reflected from the glass plate interfere with rays reflected from the surface of the lens. If white light shines onto the lens, coloured interference patterns can be seen. Though the rings now bear Newton’s name, he only developed a partial explanation for their occurrence. In fact, they were first observed by Hooke and Boyle.