Earlier it was considered that light travels through an imaginary medium called ether.
Nowadays it is known to us from the principle of relativity that no such ether medium exists in reality.
In the year 1873, Maxwell put forward the electromagnetic nature of light.
It provides us with a more powerful approach to the study of light.
From plane wave solutions, we find that the electric field and the magnetic field are both perpendicular to the direction of propagation of the wave.
Therefore, this proves that the electromagnetic wave is a transverse wave.
Further, it is also proved that the electric field and magnetic field are mutually perpendicular to each other.
We also know that a change in magnetic field induces an electric current while a change in electric field induces magnetism.
In conclusion, both electric field and magnetic field undergo a continuous change which induces the other field in a direction mutually perpendicular to each other as well as the direction of propagation of the wave, thus causing the wave to propagate forward.