RADIATION OF A POINT-CHARGE UNIFORMLY MOVING IN A DIELECTRIC MEDIUM

We analyse how the frequency dependence of the dielectric permittivity affects the electromagnetic field radiated by a point charge uniforml y moving in a medium. It turns out that a moving charge radiates at ev ery velocity. We study the space distribution of the electromagnetic f ield and show that its oscillations are due to the time-dependent pola rization of the medium induced by the moving charge. Spectral distribu tions of the radiated energy and the photon number are given. Conseque nces arising from a choice of polarization different from the usual on e are discussed. An analysis of the Kramers-Kronig dispersion relation s for the treated problem is given. This consideration may be useful f or the experiments recently discussed in the literature.