ABSTRACT
The momentum of the electromagnetic field is not treated so frequently as the field energy. In addition, the question of field momentum in a medium has often proved to lead to a certain amount of confusion since it involves a choice of expression for the energy-momentum tensor of the electromagnetic field in a medium. Energy conservation for a transparent medium with the inclusion of arbitrary frequency and spatial dispersion in a wide range was analysed, and in general has been rather frequently discussed in the literature. This is not the case, however, for the energy density and the heat liberated in a dispersive absorbing medium or for momentum conservation in macroscopic electrodynamics. The question of field momentum in a medium has often proved to lead to a certain amount of confusion since it involves a choice of expression for the energy-momentum tensor of the electromagnetic field in a medium.
