In a Newton's rings apparatus, monochromatic light interferes in the thin film of air between the slightly convex lens and a plane glass plate. The wavelengths are determined from the radii of the interference rings.
Benefits
the color of soap bubbles is based on it: interference in thin films
use interference optics to determine most subtle differences
elaborate filters make quantitative measurements possible
Tasks
Using the Newton's rings apparatus, to measure the diameter of the rings at different wavelengths and:
to determine the wavelengths for a given radius of curvature of the lens
to determine the radius of curvature at given wavelengths.