Newton's Rings
An interference pattern of concentric bright and dark rings formed by an air film enclosed between a plano-convex lens and a flat glass plate.
Governing formula
r_m² = m λ R (Dark rings in reflection)
SI unit
m
In depth
The air film thickness increases quadratically from zero at central contact point. Interference of reflected light produces circular fringes centered at the contact point.
Examples in the real world
Testing the optical surface quality and flatness of optical lenses during precision manufacturing.