Polarization of Light

11 Jul 2010


Polarization is a property of light, or other electromagnetic radiation, that is primarily understood through studying the waves of the radiation. Polarization was discovered by Etienne Louis Malus, a French physicist in the early 1800s. Light is the range of electromagnetic radiation that humans can see. The wavelengths of light have a range from 380-750 nanometers. Electromagnetic radiation is radiation that is produced by electric and magnetic fields that travel together at the speed of light through space

It is sometimes easiest to consider polarization if only one of the two sets of waves is considered the electric set. In unpolarized light, waves are in a jumble of directions. The waves have many different orientations around the direction that the light is going. Each wave is represented by an arrow that is at a right angle to the direction that the wave is moving; however, one arrow may point sideways, one may point upwards, and another may point downwards.

Although unpolarized light may be chaotic, polarization has the opposite effect. Polarized light has the orientation of all the arrows pointing in the same direction. Regardless of which direction the arrows may face, all the arrows follow suit, exactly.

Some scientists may mention circularly polarized light. In that case, the arrow representing the waves of light still exists. However, the arrow rotates as the wave moves along. Some have compared the arrow depicting the waves if circularly polarized light to a hand of a clock rotating around and around as the wave advances.

Polarization is also produced naturally in some instances. For example, when light passes through particular crystals or through artificial material designed to create a polarization effect. Polaroid is one such artificial material that is used in polarized sunglasses. Polarized sunglasses work by only letting vertical polarized light in. They are immensely popular among outdoors enthusiasts and people who wish to reduce the glare from the sun.

Radio transmission and receiver antennas also are polarized. One of the most common uses of polarization is through radar. AM and FM radios use vertical polarization while televisions use horizontal polarization. Interestingly, vertical and horizontal polarization alternates with the use of satellite communications even for television use. Therefore the satellite can carry two distinct transmissions of a frequency and double the amount of customers that can be served by one satellite.

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