Energy of Electromagnetic Waves in the Presence of Absorption and Dispersion

Abstract

Expressions for the stored energy, energy flow, and power dissipated are derived for electromagnetic waves in terms of the complex permittivity ${\epsilon }^{\prime }$ and permeability ${\mu }^{\prime }$ for a frequency-dispersive absorbing medium. This is shown to be possible when ${\epsilon }^{\prime }$ and ${\mu }^{\prime }$ are known functions not only of frequency but also of all the loss factors —e.g., collision frequencies, etc. The derivation is not restricted to media with small losses. An oscillating particle system and an electric circuit are used as illustrative examples of the application of the energy expressions derived.