When a substance has coefficient of refraction that depends on direction, a single ray of unpolarized light incident on its surface normally splits in 2 rays - no fewer except in case of specific directions where the 2 coincide, but also no more - which have different, linear, polarization. What should happen when a substance is chiral? Like biological transparent substances? It is said that chiral substances turn polarization plane. But consider that linearly polarized light can be viewed as superposition of circularly polarized lights of opposite polarization. Therefore, rotating the polarization plane of linearly polarized light is tantamount to circularly polarized lights of opposite polarization propagating at different speed. But if, in a chiral substance, light of opposite circular polarization propagates at different speed, should lights of opposite circular polarization then refract to different directions? And should chiral substances cause unpolarized or linearly polarized light to split into rays of different circular polarizarion travelling to different directions?