Liquid Crystal Displays: Fundamental Physics and Technology

4

The Polarization of an Electromagnetic Wave

In the previous chapters, the observation of double refraction of light and the polarizing effect of calcite were noted, and then light was shown to be an electromagnetic wave that when passed through a medium, was affected by the molecular structure of that medium. In the sinusoidal wave solutions to the electromagnetic wave equation, for anisotropic media, there was found a phase difference between the electric vector components of the light, and that caused a phase lag that polarized the light. The mathematical description of the polarization came from the Maxwell equations, but what does the polarization of light mean physically?

Unpolarized Light

Naturally occurring light is unpolarized, but according to solutions of the Maxwell equations given in Chapter 2, it was found that elliptical polarization is the state where there are no special correlations between the amplitudes and phases of the components of the electric vector; so what then is “unpolarized light”? The sum of the vibrations of the electric field components in natural light actually always form an ellipse (the most general form of polarization), but the polarization modes are constantly randomly changing through ellipses of different ellipticity (including lines and circles), and if the changes are more rapid than can be detected, then the light is considered unpolarized because all of the polarization effects are averaged out. In the words of Richard Feynman [1], ...