Correlation of polarized light phenomena with the orientation of some metal crystals

Abstract

A photometric study was made of t h e refl ection of plane pol ari zed li ght no rmalh' incident in a metallographic microscope upon specim ens of tin, aluminum, and monel with variou s surface treatments. A high degree of correlation was found in most c9,se~ between the extin ction position and the projection of the optic axis or of the cubic axis making the greatest angle with the surface normal. Moreo ver, a fourth power sine relationship was obser ved between the change of intensity and t he angle between t.he s urface normal and the optic ax is in t in. The inte nsity correlation in the case of the cubic metals was not so clear, but a sli ght indication of position d epend ence was obse rv ed for a luminum. The res ults indicate that the optically anisotropic effects obser ved with cubic m etals can be caused both by an isotropic fi lm s a nd by oriented surface conto urs, but that the latte r is the source of t hose effects that are correlated \\'i t h t he crystall ograph ic ori e ntation of t he grain.