Polarized sunglasses are designed to reduce the glare caused by the reflection of sunrays, particularly from horizontal planes like water, snow, flat roads, and car hoods.
They have been commonly used by fishermen and boaters as a means to minimize or block the glare reflected from water surfaces.
In recent times, as people have become more aware about the various benefits of using polarized lenses, goggles, and sunglasses, these have become very popular, especially among those spending time outdoors.
In the following lines, we shall examine the working of polarized sunglasses, and also take a look at their typical uses.
Working of Polarized Sunglasses
In order to understand the working principle of polarized sunglasses, let's discuss in brief about the reflection of light from the plain, smooth surfaces.
When light falls on a flat and smooth surface, the reflected light is directed in the horizontal planes (polarized), rather than dispersing or scattering in all directions as is the usual case. These horizontally oriented rays of light add up with each other and increase in intensity. This is experienced as annoying flashes of white, known as glare. A prolonged exposure to such light intensities may result in temporary blindness which can be very dangerous in many situations.
The polarized sunglasses comprise a film of chemical compound, which is coated on transparent glass or plastic lenses. It consists of tiny molecules that align in a parallel fashion with respect to one another.
This chemical film, allows only the light rays, having wavelengths that are not aligned with the particles of the filter to pass. In other words, these glasses block the high-intensity light rays from passing through, thus significantly reducing or even eliminating glare.
If the coating on the lens is uniform, the molecules will absorb (block) the entry of all light intensities that matches their alignment. Since glares are mostly caused by the horizontally oriented light waves, this coating is designed in such a way that it allows only the vertically polarized light to pass through.
With such polarized sunglasses, the textures and shapes of objects become more clear, irrespective of the glare. This way, polarized lenses reduces the effect of glares. One of the drawbacks is that liquid crystal displays (LCD's) may not be visible while viewing them at specific angles.
Difference Between Normal and Polarized Sunglasses
The difference between normal sunglasses and polarized sunglasses is that in the normal ones, the intensities of all light in the spectrum are reduced equally; whereas, in case of the polarized ones, only the selective intensities, that cause glares, are eliminated.
You can check whether a pair of sunglasses are polarized or non-polarized, by focusing on a reflective surface, and rotating slowly, while looking through them. If the intensity of the reflected light remains constant, then the sunglasses are not polarized. If however, the intensity drops at certain angles and rises at others, then they are polarized.
Uses of Polarized Sunglasses
These are ideal for a number of outdoor activities. These include boating, fishing, skiing, jogging, golfing etc.
These are an excellent tool while driving, to avoid glares from road surfaces, rooftops, large metallic structures, hoods of cars, etc.
They can also prove to be very useful indoors, especially for light-sensitive people such as those recovering from a cataract surgery, and for those desiring to avoid exposure to bright lights through the windows.
Polarized sunglasses are available in a wide variety of frame styles and lens colors. In addition to that, you can also opt for prescription polarized lenses, which are available in gray or brown color. While purchasing the polarized sunglasses, always opt for the ones from a reliable brand, as the poor-quality ones may not be effective in eliminating glare. In addition, you should also check for other additional features, such as ultraviolet light protection, tinting, anti-reflective and anti-scratching coatings, etc.