ABSTRACT
One of the most important solutions to the propagation equation in vacuum corresponds to plane waves, which are only functions of time and one spatial coordinate. In general, the phase of the plane is defined by the relativistically invariant quantity Such plane waves represent classical solutions to the electromagnetic wave equation, but they assume a particularly important role in electrodynamics because they offer a natural introduction to the quantum electrodynamical concept of the photon. In addition, plane wave solutions form the basis of the Fourier analysis of wave propagation, which is a powerful mathematical tool to study linear problems where the principle of superposition applies. In this respect, plane waves are closely linked to the Green functions presented in Chapter 5 and represent their natural mathematical complement.
