Interference Phenomenon in the Schlieren System*

Abstract

A diffraction phenomenon has been discovered in the schlieren system which makes possible a quantitative schlieren method. In this method bands are observed in the schlieren field. These bands represent regions in the schlieren through which the optical path length is constant and different from the schlieren free portion of the field by $(N+\frac{1}{2})$ wave-lengths of the light used (where N represents an integer). It has been demonstrated that, within the experimental accuracy, these bands have the same meaning as those observed in the Mach-Zender type of interferometer when that instrument is adjusted so that one fringe covers the entire field.