# 5.3.1: Polarized Light

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The vibration direction of a light wave (which is the direction of motion of the electric wave) is perpendicular, or nearly perpendicular, to the direction the wave is propagating. In normal unpolarized beams of light, waves vibrate in many different directions, shown by arrows in Figure 5.15.

We can filter an unpolarized light beam to make all the waves vibrate in one direction parallel to a particular plane (Figure 5.16). The light is then plane polarized, sometimes called just polarized. (Unlike the drawings in Figure 5.16, a beam of white light, whether polarized or not, may contain many different wavelengths.) Figure 5.16a shows a wave vibrating horizontally and Figure 5.16b shows one vibrating vertically. Figure 5.16c shows the two polarized rays together. They are in phase but need not be.