Sunglasses Polarization

Light waves from artificial light sources such as the sun and even light bulbs vibrate and propagate in all directions. Whether light is propagated, reflected, diverged, or refracted, when it vibrates in one or more plane directions, we say that light is polarized. The polarization process can occur naturally or artificially. The glare you see every time you observe the lake surface is an example of natural polarization. The glare reflected from the lake surface is the light that cannot pass through the "filter" of the lake water, which is why even if the lake water is very clear, objects under the lake surface cannot be seen.
Polarization filters are generally made by coating a layer of chemical thin film on a transparent plastic or glass surface. Usually, the molecules in the compounds used are naturally parallel to each other. When they are evenly coated on the lens, these molecules form tiny lenses that can absorb all the light in the same direction as their arrangement.
The vast majority of glare that forces you to wear sunglasses comes from horizontal surfaces, such as water surfaces and highways. When light reaches a surface, the reflected light will polarize in the same direction as the angle of the surface. Therefore, a highly reflective horizontal surface, such as a lake, can generate a large amount of horizontally polarized light. Therefore, the polarizing lenses of sunglasses are fixed at an angle, so that only vertically polarized light can pass through the lenses. You can observe this principle by wearing polarized sunglasses and then observing a horizontal surface, such as the hood of a car. Slowly tilt your head to the left or right. You will find that the glare from this surface will become brighter as you adjust the angle of your gaze.
Before purchasing, you can distinguish its authenticity by conducting a simple test. Find a reflective surface, then hold sunglasses and observe it through a lens. Slowly rotate the sunglasses 90 degrees and observe if the reflected glare decreases or increases. If the sunglasses are polarized, you will see a significant reduction in glare.
Sunglasses or prescription glasses that darken in color when exposed to sunlight are called color changing glasses. The principle of color changing lenses mainly relies on a special chemical reaction of ultraviolet radiation.
Color changing lenses contain millions of molecules of certain substances, such as silver chloride or silver halides. When there is no ultraviolet radiation, visible light can penetrate these molecules, and visible light is a general component of artificial light sources. But when exposed to the ultraviolet rays of sunlight, these molecules will undergo a chemical process that changes their shape. The new molecular structure will absorb some visible light, causing the lens to darken. The number of molecules with changes in shape will change with changes in UV intensity.