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Types of waves: electromagnetic waves

Beside mechanical waves, there are waves which can propagate even in the absence of any medium: electromagnetic waves. Light, for instance, represents the part of electromagnetic waves to which the eye is receptive, and which therefore is responsible for the phenomenon of vision. Without entering into many details, we will say that in the case of electromagnetic waves the propagating perturbation is an electromagnetic field, namely the combination of an electric field and a magnetic field oscillating in two planes perpendicular to one another. In the historical chronology section concerning light we briefly recall the most important discoveries concerning electromagnetic waves.

Electromagnetic waves are present everywhere in the universe and the greatest part of them is invisible to the eye. Among these we can mention X rays, ultraviolet and infrared radiation, microwaves, and radiowaves. We shall return in a while to electromagnetic waves and in particular to light. We already said that electromagnetic waves are capable of propagating in empty space. Let us add that this is very fortunate, since, if this were not the case, light and the heat of the sun could not reach the earth, and very unpleasant consequences would follow.