The thermodynamics and electrodynamics of the superradiant phase are analyzed on the basis of the Emeljanov-Klimontovich model by means of a mean field approach and random phase approximation. The model considers infinite modes of radiation field. The superradiant phase is characterized by a static and homogeneous Bose condensation of the transverse collective mode with zero wave vector. The thermodynamic quantities and the dispersion relations for the collective mode are obtained in closed forms. While the thermodynamic properties of the present model are the same as those of the Dicke model, the electrodynamics differs in form from the latter. A softening of the lower branch of the collective mode behaves as (T-Tc)1/2 for T>T_c, whereas for T<T_c it obeys a law T_c-T or (T_c-T)1/2 according to the different regions of temperature and the polarizations. A light velocity is renormalized with an anisotropic constant.