General relations between phase normal vectors, refraction vectors and ray refraction vectors
as well as between phase and ray velocities of plane waves are obtained for linear
non-absorbing optically active (bianisotropic) media. For such media the geometric constraint
on the wave surfaces is discussed. Equality of the group and ray velocities of the
monochromatic plane waves in dispersive bianisotropic media is proven. It is shown that the
degree of the ray surface equation generally exceeds the degree of the refraction surface and
phase velocity surface equations but it cannot be greater than 108. In particular, for
gyrotropic dielectric media of symmetry classes 3, , 4, ,
4/m, 6, and
6/m it equals 12. The domain of applicability of the duality principle known
in optics of anisotropic media is determined.