Answer
Interference of light waves accounts for Newton’s rings.
Work Step by Step
When a lens that is flat on one side and bulging on the other (aka a plano-convex lens, like a piece sliced off a glass sphere) is placed on an optically flat surface, and illuminated from above with monochromatic light. a series of concentric rings is seen.
The light circular bands are regions of constructive interference, when the wave reflecting off the top surface of the lower piece of flat glass is in phase with the wave reflecting off the curved bottom surface of the plano-convex lens.
The dark circular bands are regions of destructive interference, when the wave reflecting off the top surface of the lower piece of flat glass is out of phase with the wave reflecting off the curved bottom surface of the plano-convex lens.
This is discussed on page 553.
