Newton's rings

Lore & Background

Newton recorded his observations in an essay entitled 'Of Colours'. The phenomenon became a source of dispute between Newton, who favored a corpuscular nature of light, and Hooke, who favored a wave-like nature of light.

Reader's Guide

Newton's rings are significant as a clear visual demonstration of wave interference and thin-film interference, where the thin film is a layer of air. The pattern arises from the path length difference and phase changes of light reflecting from two surfaces. The central region is dark when illuminated from above due to destructive interference at the point of contact. The radial positions of the rings allow calculation of the air gap thickness and the radius of curvature of the lens. The phenomenon also illustrates the historical dispute between Newton's corpuscular theory and Hooke's wave theory of light, and it remains a standard method for testing optical flatness.

Did You Know?

• The central region of the pattern is dark when illuminated from above because the waves interfere destructively at the point of contact.
• The difference in height between two adjacent bright or dark fringes is one-half wavelength of the light used.
• When viewed with white light, Newton's rings appear as a concentric ring pattern of rainbow colors.