On conservation lows for energy and momentum in electromagnetic field in media and under plane wave diffraction on conducting plate

The general nonstationary balance equations for energy and momentum densities of field-matter system based on rigorous nonstationary approach for their definitions with dependence from the field creation prehistory have been obtained. Also the transport velocities of these densities have been derived. The concrete examination and detailed consideration have been performed for simplest dispersion low which is defined by the conductivity connected with the dissipation. There are following parameters which have been found for plane monochromatic wave under this low: the energy density, the phase velocity, the group velocity, and the transport velocities of energy and momentum. It has been shown that the energy density has the static form in which the dielectric permittivity must be replaced by its real part, and the energy transport velocity coincides with the phase velocity. The group velocity in this case may exceed the light velocity in the vacuum. It has been also shown that correct form of momentum density is the Minkowski one, and the momentum transport velocity in this case also coincides with phase velocity. The energy and momentum conservation have been shown for plane electromagnetic wave in the conducting medium and for plane wave diffraction on the conducting plate.