1. Material classification

The interaction of EM waves with material media, within which particles (electrons, ions, molecules...) are present, some of which are charged, involves various physical mechanisms that can be represented by the absolute permittivity ε, absolute permeability µ and electrical conductivity σ of the medium. Materials are classified according to the value (low or high) and nature (scalar or tensorial) of these three quantities.

The purpose of this article is not to study the electrical and magnetic properties of matter. There are many books on the subject. Readers are invited to consult the following references and