Crystal Optics With Spatial Dispersion, and Excitons : Springer : 9783662024089 : 366202408X : 18 Apr 2014 : Spatial dispersion, namely, the dependence of the dielectric-constant tensor on the wave vector (i.e., on the wavelength) at a fixed frequency, is receiving increased attention in electrodynamics and condensed-matter optics, partic­ ularly in crystal optics. In contrast to frequency dispersion, namely, the frequency dependence of the dielectric constant, spatial dispersion is of interest in optics mainly when it leads to qualitatively new phenomena. One such phenomenon has been weH known for many years; it is the natural optical activity (gyrotropy). But there are other interesting effects due to spatial dispersion, namely, new normal waves near absorption lines, optical anisotropy of cubic crystals, and many others. Crystal optics that takes spatial dispersion into account includes classical crystal optics with frequency dispersion only, as a special case. In our opinion, this