Use of Tungsten Arc Lamps for Photomicrography

Abstract

THE uniform intrinsic brilliancy and compactness of the tungsten arc lamp have led to its extensive application as an illuminant for photomicrography. It does not appear to be generally recognised, however, that the light which leaves the metal surface at angles approaching a tangent is so strongly plane polarised that it is difficult to obtain uniform illumination when crystals are being photomicrographed by plane polarised light.