The optic interference figures of Amethystine quartz. Part II

Abstract

Using a wavelength ( λ 5890) for which the linear dichroism of the amethystine sector is appreciable (k > |2σ|), twenty-four interference figures are reproduced confirming in detail the theory of light propagation in absorbing crystals possessing optical activity. Unlike the behaviour in transparent crystals, the idiophanic interference figures seen with a polariser alone in front of the plate differ in general from those presented with an analyser alone behind the plate in the same setting. The existence of four singular axes, one on either side of each optic axis, is shown: along each singular axis only one (elliptically) polarised wave- and not two- can be propagated without change of form.