So, how do sunglasses work?

There are two reasons to wear sunglasses. The first reason is if you do not like the bright sun shining in your eyes, because the dark surface of the sunglasses helps block the light and darken the world. Secondly, the sun's ultraviolet rays can be harmful in the long run because they cause all kinds of eye problems, including loss of sight and eye cancer. Good sunglasses protect against this because their lenses filter out most of the harmful UV rays.

So, how do sunglasses work? The darkening effect is a very simple one looking at the world through tinted lenses makes it seem darker to you – even though the effect is really just an optical illusion, it can help you if exposure to bright sunlight tends to give you a headache or cause you to squint.

The UV filtering effect is however more complex. UV filtering lenses are coated with special chemicals that let in the light but reflect it.  ultraviolet light   is essentially high frequency light waves, which means that the chemical structure must be constructed to deflect the light at high frequency while letting the light pass at a low frequency. It's a difficult science, and the equipment needed to do it is expensive.

The most complicated sunglasses are prescription sunglasses. These are sunglasses that not only protect from light and UV rays, but also function as normal glasses to correct your eyesight. For this to work, normal-vision glasses need to be taken, tinted and covered with UV-reflective chemicals - a complex three-step process. However, all the ingredients work together perfectly to produce portable sunglasses for people who need their vision to be constantly corrected. It is even possible to buy clear tinted lenses that fit over your normal glasses, making it a way to make custom sunglasses.