How Sunglasses Work
The
concept of sunglasses seems quite simple, a
couple of darkened lenses in a frame to block
out the sunlight. However, there is more to
sunglasses these days and good modern sunglasses
work in four major ways.
1. Provide protection from UV
(ultraviolet) rays. UV rays are emitted by sunlight and can damage the retina
and cornea in the eye. A good pair of sunglasses can completely block out all UV
rays. Beware of cheap sunglasses however as these can do more damage than good.
Cheap sunglasses block some light, allowing your iris to expand but do not block
UV rays and therefore increase your exposure to UV rays.
2. Provide protection from glare.
Glare is caused when sunlight reflects off certain surfaces such as snow or
water. These reflections can cause distractions or even obscure areas of vision
completely. Good sunglasses can remove 100% of glare. This is done by something
known as polarization.
3. Provide protection from intense
lights. Intense light can be very dangerous to the eye. When too much light is
getting into your eyes, the iris starts to close but this can only close so far.
If there is still too much light then you begin to squint in an attempt to block
out some more. If after all this, still too much light is entering the eye, then
retina starts being damaged and can lead to permanent eyesight problems. A good
pair of sunglasses can reduce the amount of light entering the eyes by as much
as 97%, vastly reducing the possibility of eye damage.
4. Block specific light
frequencies. There are particular frequencies of light that can blur your vision
or increase viewing contrast. By choosing the right color for your sunglasses
you can tailor them to specific requirements. e.g. Fishing, skiing.
In general, sunglasses allow some light
to be transmitted and some light is reflected away. This occurs at various
stages - as the light hits the outside of the lens, the interior of the lens,
and the back of the lens. Sunglasses are classified by tint, light transmittance
and UV absorption.
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