Principle

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:

1. to determine the wavelengths for a given radius of curvature of the lens
2. to determine the radius of curvature at given wavelengths.

Learning objectives

• Coherent light
• Phase relationship
• Path difference
• Interference in thin films
• Newton's ring apparatus