How do Polarized Sunglasses Work

View with and without polarized lenses

What Are Polarized Lenses?

Polarized lenses-the greatest thing since sliced bread. Invented in 1936 by Edwin H. Land, the same man who brought you the Land's camera by Polaroid, polarized lenses have long been a staple in the eyewear industry. And for a very good reason. Polarized glasses cut hazardous glare off of flat surfaces such as water, glass, and asphalt. The question this article and our sunglass lens color guide will answer is: what are polarized sunglasses and how do they work?

What Do Polarized Lenses Do?

So, what do polarized sunglasses do, exactly, and what lens color is the best for bright days? First, let's back up a little in the history of the polarized lens. In 1808, 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. When it leaves the pitcher’s hand, the ball is traveling in one trajectory, but it’s weaving and bouncing up and down, left and right, totally erratic and looking like a bundle of unpredictable energy. 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.

Infographic of how polarized light passes through a polarized lens

Stepping away from reality for a moment, but still using the metaphor of a baseball, imagine that the ball that was hit by the batter is still traveling in one direction, but while moving forward, it’s also weaving from side to side. It’s fast coming up on the outfield fence, which is a series of vertical bars. As the ball approaches, weaving left and right, it bounces off the vertical fence posts, because there’s no way it can pass through moving in a zig-zagging horizontal line.

If that same ball was instead traveling in a vertical line, moving up and down, it could easily pass through the gaps in the fence because it’s in the same alignment as the bars.

For this example, it may also help to think of light like a mattress that you’re trying to fit through a door. If the mattress is perpendicular to the door, there’s no way you’ll be able to get it through, right? But if you turn the mattress upright, it can pass through the doorway without any issue.

This vertical fence is the polarized filter in your sunglasses.

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. It can’t pass through because it’s moving the opposite direction of the filter.

Likewise, any non-polarized light that’s moving in multiple directions (i.e., the knuckleball) will become polarized as it passes through the filter, because the horizontal light will be blocked, and the vertical light will pass through.

How to Test If Your Lenses Are Polarized

If you were to take 2 of these filters and cross them perpendicularly, less light would pass through. The filter with a horizontal axis will block vertical light, and the vertical axis will block horizontal light. That's why if you take two polarized sunglasses and tilt them back and forth between 0° and 90° angles, they'll darken as you rotate them.

polarized lenses test example

You can also verify whether your lenses are polarized by holding them in front of a back-lit LCD screen. Unlike standard sunglasses or non polarized sunglasses, 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. The screen in the video below has a filter on a horizontal axis, which is why the lens does not darken until fully vertical.

polarized lens test with screen

Protecting Your Eyes From The Summer Sun

Most outdoor enthusiasts are well-versed in ways to protect their skin from the sun but a little bit of preventative eye care can go a long way to prevent any eye strain or eye damage from bright light. Protect yourself from preventable damage to your eyes with these simple tips and insights.

Not all sunglasses are equal. Cheaper lenses on regular sunglasses let less light into your eyes but fail to block the UV rays you can't see. UV rays can do serious, long term damage to your eyes. Make sure your lenses block 100% of both UV-A and UV-B rays. UV-A and UV-B rays make it through the protective ozone layer, and can cause long-term damage to your eyes.

While many lenses feature a protective UV coating that quickly degrades after time, Revant lenses provide integrated UV protection within the lens itself that keeps your eyes safe from 100% of UVA, UVB and UVC rays for the life of your lenses.

Do polarized sunglasses protect your eyes better?

Not exactly. While they do elevate contrast that will enhance situations where glare can be distracting or dangerous, they don't offer any additional protection from harmful UV rays. However, polarized, tinted sunglasses’ glare reducing properties can alleviate the onset of sunlight-induced eye strain and headaches.

What are the disadvantages of polarized sunglasses?

The most often talked about disadvantage of polarized lenses is that they can make it difficult to look at LCD screens. While wearing polarized lenses, the lenses reduce the amount of light your eyes process from an LCD screen. In certain conditions your phone screen might be visible when looking at it at a 90 degree angle, moving to different angles can make the display disappear completely.

Are polarized lenses good for driving? Not for everybody. The treatments in automotive glass can also be slightly more apparent while wearing polarized lenses, causing some minor distractions while driving. 

Upgrade to Polarized Lenses

At Revant, we specialize in making polarized replacement lenses for any brand of sunglasses. If you have an old pair of non-polarized sunglasses that need to be refreshed or upgraded, we can help. If you’re looking for the best sunglasses for watersports, polarized sunglasses might be your answer. Check out our full assortment of polarized lenses in the link below.

Shop Polarized Replacement Lenses

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