ABSTRACT
Fabry-Perot interferometer consists of two semi-silvered glass plates. Multiple-beam fringes of the air film contained between the two plates, are observed. One glass plate is fixed and the second is mounted on a moveable carriage. The two glass plates are made parallel by means of screws provided for the purpose. Air film comprised between two glass plates the opposite faces of which are semi-reflecting and parallel. The semi-reflecting films on the glass plates are deposited with this in view; thus materials with as low absorbence as possible are used. An air wedge of angle formed between two plates, is illuminate by a parallel beam under normal incidence. The fringes are visible in white light. The central fringe is white with coloured fringes on either side.
