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Polarization

The case shown in Fig. 14.7 is linearly polarized, which means simply that the $\Vec{E}$ and $\Vec{B}$ fields are in specific fixed directions. Of course, the directions of $\Vec{E}$ and $\Vec{B}$ could be interchanged, giving the ``opposite'' polarization. Polaroid sunglasses transmit the light waves with $\Vec{E}$ vertical (which are not reflected efficiently off horizontal surfaces) and absorb the light waves with $\Vec{E}$ horizontal (which are), thus reducing ``glare'' (reflected light from horizontal surfaces) without blocking out all light.

There is another possibility, namely that the two linear polarizations be superimposed so that both the $\Vec{E}$ and $\Vec{B}$ vectors rotate around the direction of propagation $\Hat{k}$, remaining always perpendicular to $\Hat{k}$ and to each other. This is known as circular polarization. It too comes in two versions, right circular polarization and left circular polarization, referring to the hand whose fingers curl in the direction of the rotation if the thumb points along $\Hat{k}$.