Interference using centimetre waves
This experiment works as a model of what is happening with light in a thin air film, or thin film reflection of microwaves in their own right.
Apparatus and materials
Microwave receiver amplifier
Glass plates, 2
Health & Safety and Technical notes
Modern equipment using a solid-state diode transmitter is safe. Older equipment using a klystron tube uses hazardous voltages. The connectors on the leads between the transmitter and the power supply MUST be shielded types to minimize the risk of serious electric shock. The ventilation holes in the power supply may also give access to hazardous voltages, so its use MUST be closely supervised.
Alternatively, one plate of glass or Perspex and one metal plate can be used.
Glass plates should be 25 cm square.
a First show that microwaves are partially reflected and partially transmitted by a single glass plate.
b Then set up the transmitter, receiver, and plates as illustrated, and demonstrate the interference between the waves reflected by the first and second glass plates.
c Show the effect of reducing the thickness of the 'film' (the distance between the plates).
This experiment was safety-checked in February 2006