The Symmetry and Optical Phenomena

The explicit forms of the broken (by a electric field E, magnetic field H and spatial dispersion of wave vector k) point symmetry groups of a crystal are given. For these groups the dielectric permeability tensors: ε$\text{}_{ij}$(ω, E), ε$\text{}_{ij}$(ω, H) and ε$\text{}_{ij}$(ω, k) - the particular cases of ε$\text{}_{ij}$(ω, E, H, k) - are written out (the susceptibility tensors χ$\text{}_{ij}$(ω, E), χ$\text{}_{ij}$(ω, H) and χ$\text{}_{ij}$(ω, k) take the same forms). In order to illustrate the results obtained the electrooptical phenomena (connected with the tensors ε$\text{}_{ij}$(ω, E)) are discussed