A simple microwave interferometer capable of measuring small phase shifts is described. The interferometer can easily be incorporated in an undergraduate laboratory. The interferometer is used to determine the relative refractive indices of gases to within a few parts per million. Analysis of the reflection in the test chamber can provide an interesting extension to the usual treatment of multiple reflections.

Topics
Microwave frequencies, Interferometry, Optical properties, Educational assessment, Laboratories
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© 1976 American Association of Physics Teachers.
1976
American Association of Physics Teachers
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