Polarizing Light

On the right is a cartoon representation of how polarizing filters work and what they do. The double arrowed lines represent, in only two dimensions, random electrical fields of a light wave. In fact, these electrical fields are in all directions perpendicular to the direction of light wave propagation. The effect of a polarizing filter is to restrict the electrical field to a single plane. The angle of this plane depends on the angle of the filter relative to the direction of light propagation.

The maximum amount of light transmitted through the two Polaroid filters occurs in #1 because the orientation of both Polaroid filters is the same. In #2 the orientation of the filters differs by 90 degrees, so no light gets through. In #3 they differ by 45 degrees so some light is transmitted.

Perceptually, the light would appear brightest in #1, absent in #2 and dim in #3.

The second polarizing filter on the right is often called the "analyzer."

More information on polarization of light

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