Scientists Say: Polarized light

Light is polarized when all its waves wiggle at the same angle 

Light can become polarized when reflecting off flat surfaces like puddles and pavement. Polarized sunglasses can then specifically block out those polarized light waves, reducing the glare that reaches a driver’s eyes.

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Polarized light (noun, “POHL-uh-ryzd LYT”)

Light is made up of waves. They wiggle as they zip through space. They can wiggle up and down, left and right, and any angle in between. Light is polarized when its waves all wiggle at the same angle.

Light sources from lamps to stars typically give off light waves that wiggle at a range of different angles. This jumble of waves is known as unpolarized light. Polarized light, on the other hand, is unjumbled: its waves all wiggle the same way, at the same angle. (For help picturing this, check out the artist’s depictions at 1:30 in this PBS video.)

Polarization is the process of turning unpolarized light into polarized light. There are a few ways this can happen.

Light can become polarized when it bounces off of a surface. The amount that it is polarized depends on the angle at which the light hits the surface. It also depends on what the surface is made of.

Sunlight reflecting off water, for instance, can become polarized. The incoming light waves from the sun wiggle all different ways. But the light waves that bounce off the surface of the water are all mostly wiggling at the same angle. Pavement is another surface that can polarize reflected light.

Another way to polarize light is to pass it through a filter. Such filters are made up of molecules that are all aligned the same way. This allows only light waves wiggling at specific angles to pass through. For example, some sunglasses contain polarizing filters. These glasses help reduce the amount of reflected light — or glare — that reaches a wearer’s eyes. That can block out glare from roadways or puddles to help protect drivers’ eyes and allow them to see more clearly.

Light can also become polarized as it passes from one type of material into another. This is a process called refraction. And light can become polarized when it bounces, or scatters off atoms as it passes through a substance. This happens to moonlight and sunlight that travels through Earth’s atmosphere.

Without tools like sunglasses, humans typically can’t detect the polarization of light. But other animals can. Examples include mantis shrimp, fiddler craps and some beetles, birds and fish.

In a sentence

Some fish camouflage themselves with polarized light.

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Maria Temming is the assistant editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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