Electromagnetic waves are transverse in nature is evident by

The phenomenon in which the vibrations of a wave are restricted in a direction perpendicular to the motion of a wave is known as the polarization of a wave. The waves for which the direction of vibration of the particles in the medium is perpendicular to the direction of motion of the wave is known as transverse wave. This shows that the polarization of waves is possible only for transverse waves. Therefore, the transverse nature of the electromagnetic wave is evident by the phenomenon of polarization.