ABSTRACT
The interferometer is illuminated by normally incident light using a point source. A number of images of this source are observed through the beam splitter and the compensating plate. The inclination of the compensating plate is adjusted by means of a screw so as to superpose the various images. The interferometer is illuminated by an extended source. Having adjusted the interferometer for circular fringes at infinity, it suffices to incline one mirror with respect to the other. The straight line fringes of the air wedge are thus observable. If the beam splitter and the compensating plate are accurately parallel, the rings at infinity are circular. On decreasing the diameter of the source, the contrast of the fringes increases though there is less light in the interference pattern.
