PURPOSE: To illustrate two-slit interference using microwaves.

DESCRIPTION: Microwaves from the source at the right pass through a pair of slits and interfere in the region to the left of the slits. The interference pattern is picked up by a microwave receiver and displayed for the class using the overhead projector microammeter. The photograph at the left shows the receiver at the central maximum; in the center photograph the receiver is at the first side minimum.

SUGGESTIONS: An effective technique to create discussion is to initially place the receiver at a nodal line for the two-slit interference pattern. The intensity increases when either slit is closed, as seen in the photograph at the right!

See Question of the Week #146 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 6D10.20)

EQUIPMENT: microwave transmitter, double slit, microwave receiver with overhead projector meter.

SETUP TIME: 5 min.