How do polarized sunglasses reduce glare

Nonmetallic surfaces, such as black plastic, tend to reflect light that is vibrating parallel to the surface and transmit or absorb light vibrating in all other directions. If the black plastic is horizontal, then it reflects light that is vibrating horizontally, creating horizontally polarized light.

The horizontal black plastic reflects less light that is vibrating vertically. The polarizer lets through light vibrating in one direction and absorbs light vibrating in all other directions. When the black surface is horizontal, the reflection looks dimmest when you hold the filter so it lets through just vertically vibrating light. The reflection looks brightest when you hold the filter so it lets through just horizontally vibrating light.

Horizontal surfaces in the environment, such as the asphalt of a street or the surface of a lake, reflect light that is vibrating horizontally. Polarizing sunglasses absorb this horizontally oriented glare. If you tilt your head sideways, this horizontally oriented glare passes through the glasses, making the surface look brighter.

Click to enlarge the diagram below. With polarized light, you can make a stained glass window without glass. Polarized light passing through sugar water reveals beautiful colors.

Attribution: Exploratorium Teacher Institute. Connect with us! Get at-home activities and learning tools delivered straight to your inbox. Invented in by Edwin H. And for a very good reason.

Polarized lenses cut hazardous glare off of flat surfaces such as water, glass, and asphalt. The question this article will answer is: how do polarized sunglass lenses work? In , a French physicist and mathematician by the name of Etienne-Louis Malus discovered that light waves from the sun, which usually vibrate in all directions, can be aligned in one direction when reflected off something. One way to understand this is to think of light like a knuckleball.

But if the bat connects solidly, the ball will go soaring back out, spinning gracefully without any of that erratic motion. In the same way, light that is reflected off a horizontal surface loses its erratic motion and travels in one concentrated beam in a horizontal motion.

This is what we perceive as glare. But if you turn the mattress upright, it can pass through the doorway without any issue. When the polarization axis is vertical, all light that has been polarized through reflection and is now traveling horizontally such as the glare off of water or a windshield , will be blocked by the filter. If you were to take 2 of these filters and cross them perpendicular to one another, less light would pass through.

The filter with a horizontal axis will block vertical light, and the vertical axis will block horizontal light. You can also verify whether your lenses are polarized by holding them in front of a back-lit LCD screen.

As you turn the lens, it should become darker. This is because LCD screens use crystal filters that can rotate the polarization axis of light as it passes through. The liquid crystal is normally sandwiched between two polarizing filters at 90 degrees to each other.

Although not standard, many polarized filters on computer screens are oriented at a 45 degree angle. You can see an example of natural polarization every time you look at a lake.

The reflected glare off the surface is the light that does not make it through the "filter" of the water, and is the reason why you often cannot see anything below the surface, even when the water is very clear. Only the part of the light wave that is not aligned with the slots in the filter can pass through. Everything else is absorbed. The light coming through the filter is considered polarized. Polarized filters are most commonly made of a chemical film applied to a transparent plastic or glass surface.

The chemical compound used will typically be composed of molecules that naturally align in parallel relation to one another. When applied uniformly to the lens, the molecules create a microscopic filter that absorbs any light matching their alignment. Most of the glare that causes you to wear sunglasses comes from horizontal surfaces , such as water or a highway.

When light strikes a surface, the reflected waves are polarized to match the angle of that surface. So, a highly reflective horizontal surface, such as a lake, will produce a lot of horizontally polarized light.

Therefore, the polarized lenses in sunglasses are fixed at an angle that only allows vertically polarized light to enter.