Thus,
around the middle of the nineteenth century, the wave theory seemed
to be very well established The only major difficulty was that since it
was thought that a wave required a medium for its propagation, how
could light waves propagate through vacuum This was explained
when Maxwell put forward his famous electromagnetic theory of light Maxwell had developed a set of equations describing the laws of
electricity and magnetism and using these equations he derived what
is known as the wave equation from which he predicted the existence
of electromagnetic waves*