Oct 14 2014
The polarization of a light wave is defined as a type of orientation of oscillations of the wave with respect to the direction of propagation of the wave.
Most of the common visible light sources including fluorescence and thermal radiation generate incoherent light waves. This radiation is produced independently by a large number of molecules or atoms with random polarization angles. Under this condition, the light is said to be unpolarized.
The electric field of the unpolarized light moves in all directions and undergoes phase changes over the coherence time of the two light waves. At any particular wavelength, a partially polarized light can be described as a mixture of polarized and unpolarized light.
In unpolarized light, vibrations take place randomly in directions perpendicular to the direction of the wave. The electrons within the atoms of the light source undergo rapid transitions thereby producing a light wave for a short interval of time.
Therefore, the resultant wave consists of a number of waves that originate at random times from atoms arranged relative to each other. The amplitudes of vibrations of these waves are equal.
Unpolarized light, in general, consists of polarized components in all directions perpendicular to the direction of propagation of the wave.
On resolving each of these polarization directions into components along with directions that are mutually perpendicular to each other, unpolarized light can be considered as two perpendicular plane-polarized beams with equal magnitude. Thus, when the unpolarized light is transmitted through a polarizer, polarized light can be obtained.
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