Light, Sound and Waves

Interference using centimetre waves

Practical Activity for 14-16 PRACTICAL PHYISCS


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 transmitter
  • 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.

Read our standard health & safety guidance

Alternatively, one plate of glass or Perspex and one metal plate can be used.

Glass plates should be 25 cm square.


  1. First show that microwaves are partially reflected and partially transmitted by a single glass plate.
  2. 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.
  3. Show the effect of reducing the thickness of the 'film' (the distance between the plates).

Teaching Notes

This experiment was safety-tested in February 2006

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