Polarization

POLARIZATION

In an electromagnetic wave, the direction in which the electric field's amplitude vector points, specifies the geometrical orientation of the oscillation. The direction of is now called the polarization of the wave.

Fig. 2.8 shows an electromagnetic wave with its electric field oscillating parallel to the vertical 'y' axis. The plane containing the vectors is called the plane of oscillation of the wave.

Hence the EM wave is called as plane-polarized parallel to the y axis. The wave's polarization can be represented by two arrows, indicating that its electric field oscillates vertically. It is continuously changing between directed up and down along the y-axis.

Thus the amplitude vector cannot point in arbitrary direction for EM waves. This is because as Gauss law for electric field for a system with a varnishing charge density

implies that

So, if we consider a wave solution for the electric field,

cannot have an oscillating amplitude in the x-direction since Due to this fact, EM waves cannot be polarized in the direction they are travelling. So EM waves are never longitudinally polarized.