The Dispersion and Absorption of Electromagnetic Waves

The topic to be reviewed in this article is the experimental study of the behaviour of matter under the action of the electromagnetic fields encountered in the electrical portion of the spectrum, that is to say, in waves of all wavelengths greater than a few millimetres. The special properties of magnetic materials will not be considered; we shall confine our attention to the action of the electric field, or to those reactions usually referred to as the dielectric behaviour of materials.