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* From the wave equation, Maxwell could
calculate the speed of electromagnetic waves in free space and he found
that the theoretical value was very close to the measured value of speed
of light