If you want sunglasses to be easy to use and stylish, they must be polarized! Here's a tip to help you identify polarized sunglasses!

The summer sun shines brightly, traveling 150 million kilometers just to reach people's faces and bring warmth.

But it will also pass through roads, water surfaces and glass curtain walls, with twists and turns that will make you dizzy and even cause disasters!

Image source: soogif

To avoid interference of strong light to vision, experienced drivers will prepare a pair of sunglasses in the cab; experienced athletes will also wear sunglasses when skiing, surfing and outdoor activities. But in fact, ordinary sunglasses are not fully competent for this job, and the burden is finally handed over to polarized sunglasses.

So what is the difference between polarized sunglasses and ordinary sunglasses? How do they filter out glare? In what scenarios can we use them? And how can we tell whether the sunglasses we buy are polarized?

Image source: soogif

01What is the difference between polarized sunglasses and ordinary sunglasses?

When talking about the working principle of sunglasses, let's first look at a visitor from afar - sunlight. The essence of light is an electromagnetic wave, and sunlight contains many irregular electromagnetic waves, vibrating in all directions in a disorderly manner, like a group of displaced refugees.

In order to prevent the damage of various waves of light including ultraviolet rays to the eyes, sunglasses came into being. The reason why ordinary sunglasses can protect the eyes from damage by ultraviolet rays is that the lenses contain one or more special materials, which are like a wall, which can accommodate or block some "refugees", reduce the intensity of light, and thus protect the eyes.

Image source: Pixabay

However, when disordered sunlight passes through specific substances and vibrates in a single specific direction after scattering, refraction, and reflection, it may form ordered polarized light, just like a well-trained army after being baptized on the battlefield.

When we are driving, skiing, surfing or even in our daily life in the city, the light reflected from the water, snow and glass curtain wall is polarized light. At this time, ordinary "walls" seem to be powerless, and polarized glasses can make up for this deficiency and play a protective role in filtering out polarized light.

Therefore, although both polarized sunglasses and ordinary sunglasses can protect your eyes from wind, rain and light, the difference is that polarized sunglasses can reduce reflected polarized light, protecting drivers, athletes and outdoor enthusiasts.

02Why can polarized sunglasses filter out glare?

What is glare? Simply put, it is a visual state caused by uneven brightness distribution in the field of vision, which leads to eye discomfort or pain. Polarized light is the culprit, and polarized sunglasses can block polarized light.

How do polarized sunglasses block light? The key lies in a small light-filtering coating or device - the polarizer.

Let's compare polarized light to two enemy phalanxes marching forward. phalanx A jumps up and down vertically, and phalanx B swings left and right horizontally. There is a vertical gate in front of them. In this case, only phalanx A can pass through, while phalanx B is blocked because of the wrong direction. The number of enemy troops that finally reach the end is greatly reduced. Just like our polarized light, the light reaching the rear after passing through the polarizing fence is reduced, and the glare symptoms can also be improved.

03What scenarios are polarized sunglasses suitable for?

Polarized sunglasses can not only reduce the intensity of direct sunlight, but also block the reflected orderly light.

When driving a car, it can effectively reduce the reflected light from the road and windows, improving driving comfort and safety.

When surfing or diving, it can reduce the intensity of light reflected from the water or sea surface, improving the clarity of vision and perception of the surrounding environment.

When skiing or snow hiking, it can reduce the reflected light from the snow and effectively avoid light damage such as snow blindness.

Therefore, when you need to protect your eyes by reducing the intensity of reflected light in your life and work, and improve your vision clarity in a strong light environment, wearing polarized sunglasses is a wise choice.

04How to identify whether the sunglasses you buy are polarized sunglasses

Open some shopping apps and search for sunglasses, and you will find tens of millions of options. Entering the sunglasses market, the dazzling array of products is overwhelming. So how do we identify polarized sunglasses?

1. Consultation: Consult an ophthalmologist or a professional optometrist.

2. Check: Check the tag or lens logo of the sunglasses product to see if it is marked as polarized sunglasses or polarized lenses. Polarized sunglasses are usually marked with "Polarized" or the abbreviation "POLA" or "P" on the product.

Source: Taken by myself

3 Test: Prepare a polarized test piece and a bright enough background light source. Under the background light source, hold the polarized test piece vertically in front of your eyes, and then observe the pattern or text on the test piece through sunglasses. If you are using polarized sunglasses, you can see a cross or grid pattern on the polarized test piece, which cannot be observed with the naked eye.

4. Observation: Since the light provided by the LCD screen is also polarized light, we can use this to verify the effect of polarized sunglasses.

Here we assume that the screen provides vertical polarized light, and a vertical fence is set inside the sunglasses. When the fence gradually rotates from longitudinal to horizontal, the electromagnetic waves swinging up and down are blocked, and the light that passes through gradually decreases or even disappears.

Therefore, when we pick up the sunglasses, point them at the computer or TV, and rotate the sunglasses, the pattern on the display gradually darkens or turns completely black due to the combined filtering effect of the LCD screen and the polarizing film inside the sunglasses. The sunglasses may be polarized sunglasses.

Source: Taken by myself

Similarly, we can also prepare two sunglasses, overlap each other, and then rotate one of the sunglasses. When the two are perpendicular, the fences inside the sunglasses also become vertical, which can pass through the up and down waves of the first longitudinal fence but cannot pass through the horizontal fence of the second one; similarly, the left and right electromagnetic waves that pass through the first horizontal fence cannot pass through the longitudinal fence of the second lens.

Therefore, if the field of vision is completely dark, it proves that both pairs of glasses are polarized sunglasses.

Source: Taken by myself

Friends who have read this, if you happen to have a pair of sunglasses, you might as well test whether it is polarized sunglasses.

The sunglasses may look dark in color, but underneath them lies a colorful life.

They are athletes chasing their dreams, drivers returning home, and brave explorers;

Wherever you look, you can only appreciate the world with a better vision.

Source: Chongqing Science and Technology Museum

Author: Wei Yi, one of the top ten science popularization ambassadors in China, Zhou Sujun, senior optometrist

Review experts: Huang He, Li Chunli, Xu Xiaoping

Statement: Except for original content and special notes, some pictures are from the Internet. They are not for commercial purposes and are only used as popular science materials. The copyright belongs to the original authors. If there is any infringement, please contact us to delete them.