105Chapter 12Electromagnetic Radiation and
Wave Behaviour
Faraday’s concept of the electric and magnetic field was a great aid to his
experimental work. Faraday’s field concept, however, was absolutely
crucial to the mathematical and theoretical work of James Clerk
Maxwell. Maxwell was able to express all the laws of electricity and
magnetism in terms of four very simple equations, which relate the
electric and magnetic fields and show their intimate connection. In fact,
from the symmetry of his equations, he predicted that, in analogy to
Faraday’s law of electric induction in which a changing magnetic field
creates an electric field, that a changing electric field would create a
magnetic field. This prediction of magnetic induction, i.e. the induction
of a magnetic field by a changing electric field was immediately
confirmed by experimental work and verified the validity of Maxwell’s
equations.
Maxwell was able to obtain still a more significant insight into
electromagnetic phenomenon from the study of his equations. He
discovered the existence of a solution to his equations in which there is
an absence of charge and in which the electric and magnetic fields
behave like a wave. He associated this solution with the phenomenon of
light, which he recognized as electromagnetic radiation. As a result of
this insight, he was able to explain the emission, absorption and
propagation of light.
The concept of an electromagnetic wave is easy to understand once
its relation to electric and magnetic induction is realized. Consider an
electric field oscillating at some point in space. Then, by magnetic
induction, (or since a changing electric field produces a magnetic field)
the oscillating electric field creates a magnetic field perpendicular to
itself in its immediate neighborhood. This oscillating magnetic field,