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If the polarization of all the electromagnetic waves in a light beam is such that each of the electric or magnetic field vectors have the same orientation, then the light beam is said to be polarized. If the light is linearly, or plane-polarized, the electric field of the light is confined to a single plane along the direction of propagation.
The second polarization state is referred to as circular polarization. Circular polarization is a little more complex than linear polarization as the total, resulting electric field of the light is such that it forms a circle. The total electric field is composed of two perpendicular linear components that have a phase difference between them of π/2. To form a circle, the two components must have equal magnitude.
Circular polarization can be further classified according to the rotation. Looking at the incoming light wave, if the electric field vector of the light appears to be rotated in a clockwise direction, then the wave is referred to as right-circularly polarized. On the other hand, if the light vector appears to rotate in a counter-clockwise direction, then the wave is said to be left-circularly polarized.
The third state of polarization is called elliptical polarization. Elliptically polarized light consists of two light waves that are linearly polarized, but unlike circularly polarized light, they have unequal amplitudes but the same frequency. This results in a light wave with electric vectors that both rotates and changes its magnitude. An elliptical shape can be traced out by the tip of the electric field vector, and therefore it is referred to as elliptical polarization. This is a special case of circular polarization.
This article was updated on the 28th January, 2020