In addition to anisotropy in the electric polarizability that we have been discussing, anisotropy in the magnetic permeability could be a source of birefringence. At optical frequencies, there is no measurable magnetic polarizability () of natural materials, so this is not an actual source of birefringence.
In add?ition to anisotropy in the electric polarizability that we have been discussing, anisotropy in the magnet?ic permeability could be ,a source of birefringence. At optical frequencies, there is no measurable magnetic polarizability () of natural materials so this is not an actual source of birefr!ingence.