Polarized sunglasses block glare in sunlight, thereby protecting the eyes from UV damage. This is all due to the polarized film filter made of metal powders (such as iron, copper, nickel, etc.), which “combs” messy light into organized light as it enters, making the light reaching the eyes softer.
Polarized sunglasses can selectively absorb specific wavelengths of sunlight by using fine metal powders (iron, copper, nickel, etc.). In fact, when light hits the lens, it is reduced through a process called “destructive interference”. That is, when certain wavelengths of light (such as UV-A, UV-B, and sometimes infrared) pass through the lens, they cancel each other out on the inner side of the lens (facing the eyes). The overlapping of light waves is not random: the peak of one wave meets the trough of a nearby wave, leading to cancellation. Destructive interference depends on the lens’s refractive index (the degree to which light bends when passing through different materials from air) and its thickness. Generally, the thickness of the lens changes little, while the refractive index varies with differences in chemical composition.
Polarized sunglasses provide another mechanism for eye protection. The reflected light from asphalt roads is a specific type of polarized light, which differs from direct sunlight or light from any artificial source in terms of order. Polarized light consists of waves vibrating in one direction, while ordinary light consists of waves vibrating in random directions—similar to the contrast between a chaotic crowd and soldiers marching in step. Reflected light is generally ordered, and polarized lenses are particularly effective at blocking it due to their filtering function. These lenses allow only polarized waves vibrating in a specific direction to pass through, “combing” the light. For road reflections, polarized sunglasses reduce light transmission by blocking waves vibrating parallel to the road. In fact, the long molecules of the filter layer are oriented horizontally, absorbing horizontally polarized light. This eliminates most reflected light without reducing the overall illumination of the surrounding environment.
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