When a charged particle is stationary, an electric field ( E) is formed around it. Again , if a charged particle continues to travel at the same speed, then a magnetic field ( B) is created around that particle. Electromagnetic waves are formed by the combination of electric field and magnetic field. In this wave the vibrations of the electric field and the magnetic field are perpendicular to each other and they are both perpendicular to the direction of wave flow. So , light is a kind of transverse wave. Convergence requires a substance through which light enters, emitting light only as a vibrating wave along a certain surface. These substances or devices are called polarizers.