Purpose:Interference of a laser beam using Fresnel's mirror.
Description:Fresnel's mirror consists of two adjacent nearly parallel dielectric plates. The laser beam reflects at a small angle off the two plates to create interference on a distant screen. The angle of one of the plates can be independently varied about a vertical hinge in the center of the mirror. A 5cm focal length convex lens is used to focus the interference pattern on a nearby screen. Note that the center of the pattern is a bright line because the two reflections are in phase.