The Resolving Power and Intensity Relationships of the Fabry Perot Interferometer with Silvered Reflecting Surfaces

By the use of a Fabry Perot etalon with very small spacing, the widths of the interference fringes were measured under conditions where the light could be considered as practically monochromatic. In this way, the resolving power which can be achieved with silver deposits of known optical density was determined for light of five different wavelengths between 6438 and 3610 A. The results can be used for selecting the most favourable thickness of silvering of etalon plates, namely that which gives the resolving power required for a given purpose without unnecessary loss of intensity. The application of the results to multiple etalons is discussed.