polarized light

[ pōlə-rīzd′ ]
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Light that is reflected or transmitted through certain media so that all vibrations are restricted to a single plane.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.


What is polarized light?

Polarized light is light that has its vibration limited to one plane.

Light is radiation in the form of an electromagnetic wave. A wave of light will move in a particular direction. As it moves, it also vibrates in different directions. These vibrations oscillate, that is, they repeatedly move in one direction and then in the reverse direction, as a pendulum does. For this reason, we say that the vibration occurs on a plane. Because light exists in three-dimensional space, these vibrations can occur on diagonal planes that go in every direction, as well as on horizontal or vertical planes.

In polarized light, the light wave vibrates on a single plane. For example, it might vibrate on a horizontal plane and not a vertical or diagonal one. A laser is an example of polarized light. Light that vibrates randomly or in every direction is called unpolarized light. Light from the sun, for example, is unpolarized light.

The process of turning unpolarized light into polarized light is called polarization.

Why is polarized light important?

The term polarized light has been used at least since the 1810s. Danish scientist Erasmus Bartholin is often credited with the discovery of light polarization. Bartholin noticed that double refraction could cause light to be split into numerous beams of polarized light. Later scientists built on Bartholin’s work, such as French scientist Étienne-Louis Malus, who discovered that reflection could also produce the polarized light that Bartholin observed.

Polarized light has a variety of uses. For example, sunglasses use polarized lenses with chemicals applied to them that act as light filters. The sunglasses only allow one plane of vibration to hit your eyeball. This causes the unpolarized sunlight to become polarized light, which makes the light appear much dimmer and less intense.

3D movies also use polarized light. When you watch a 3D movie, you are actually watching two different movies simultaneously projected from two different cameras. 3D glasses have two different light filters (one on each lens) that separately filter the light from each movie into polarized light. Each of your eyeballs is seeing a different vibration of polarized light, which causes the illusion of depth.

Did you know ... ?

The trademark Polaroid refers to a brand of material that produces polarized light. If you ever see this trademark mentioned in reference to a certain item (such as a camera), you can be pretty confident that the item makes use of polarized light.

What are real-life examples of polarized light?

Polarized light is used in a number of different technologies. In particular, cameras and lenses use or manipulate polarized light to make much clearer images.


Quiz yourself!

True or False?

In polarized light, the wave of light is vibrating in random directions.

How to use polarized light in a sentence