→The only major difficulty with wave theory 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 electro magnetic theroy of light.
→ He 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 electro magnetic waves.
→From the wave equation, he calculated the speed of Electro magnetic waves in free space and he found that the theoretical value was very close to the measured value of speed of light.
→From this, he propounded that light must be an electro magnetic wave.
→Thus, according to Maxwell, light waves are associated with changing electric and magnetic
fields. Changing electric field produces time and space varying magnetic field, and a changing magnetic field produces a time and space varying electric field.
→The changing electric and magnetic fields result in the propogation of electromagnetic waves (or light waves) even in vacuum.