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Unformatted text preview: Why is the disparity in magnitudes? Answer : This disparity is illusory, and reflects only our choice of units. Polarization The direction of the E field of an EM wave is defined to be the direction of the polarization . The polarization plane is the plane spanned by the electric field and the Poynting vector, or the direction of propagation of the wave. When the polarization is unchanging, i.e., the elec- tric field in a wave always points in the same direction, we say the wave is linearly polarized . The direction of the electric field does not have to remain in the same direction, but can rotate clockwise or counterclockwise (with respect to the Poynting vector). If the magnitude of the electric field is constant while it rotates we say the wave is circularly polarized . If not, it can be elliptically polarized . Waves dont have to be polarized. We say that a wave is unpolarized if the the polarization direction is random. That is, at each moment of time the polarization randomly jumps from one direction to another. This typically happens when we have a natural source, although some natural sources have partial polarization. Sunlight is generally unpolarized (random polarization): The net fields are E total y and E total z . For truly unpolarized light | E total y | = | E total z | . The most common type of polarizer is the polaroid sheet. It is made of parallel conducting wires. At the molecular level these are normally polymers, which are long macromolecules of chains of structural units. The polaroid works such that the component of the electric field in the same direction of the wires is absorbed or reflected, and only the component of the electric field perpendicular to the wires is transmitted (this direction is called the transmission axis ). Therefore, if light in front of the polaroid was unpolarized, the light behind it would be polarized....
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