What Are Sunglasses?
And How Do They Work?
By: Cole Hoffman
Sunglasses
There are three main types of sunglasses. Common or simple sunglasses have thin plastic or
sunglasses.jpg
Picture 1 Pair of common sunglasse

glass lenses that absorb most of the light entering your eye. sunglasses in addition to absorbing light they cut out bright glare. Photochromic lenses contain substances that make the lens darken in sunlight.



Polarized Sunglasses
Polarized sunglasses not only dim the light, but also cut out bright glare reflecting off of shiny surfaces. Polarized lens blocks all rays except those vibrating in a certain plane. Here's an example:
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Picture 2 diagram of polarized sunglasses




UV Light
Ultraviolet radiation is invisible to the human eye. It is emitted from some high-temperature surfaces such as the sun. The UV spectrum is divided into two parts near/soft and far/hard. Near/soft UV radiation is produced by special fluorescent lamps to promote plant growth. Far/hard UV radiation is used to kill germs and bacteria in places where a sterile environment is crucial. UV radiation can produce direct and indirect effects on the human body. Direct effects include: sunburn, suntan, and progressive adaption to heavier doses. UV burns can be mild causing tenderness and redness or could be so severe as to produce blisters, swelling, seepage of fluid, and sloughing of the outer skin.


What to Look For
When you’re buying sunglasses you should make sure you get a pair that will help your eyes. A good pair should provide protection from UV light, protection from intense light, protection from glare, and eliminate specific frequencies of light. Some of the technology used to do this are: tinting, polarization, photochromic lenses, scratch resistant coating, anti-reflective coatings, and UV coatings.
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Picture 3 What makes up a good pair of sunglasses lens

Glossary

Ultraviolet radiation- light invisible to humans that can cause serious burns and be harmful to the eye.

Polarized lens- lens that not only dim light but also blocks glare.

Photochromic lens- lens that turn dark in sunlight. Usually used for people who need prescription lenses.

Citations
Ardley, Neil. How Things Work. Pleasantville: Readers Digest, 1995. Print
Brain, Marshal. How Stuff Works. New York: Hungry Minds, c2001. Print
Macaulay, David. The Ways Things Work. Boston: Houghton Mifflin, 1988. Print.

Heiting, Greg. “Ultraviolet (UV) Radiation and Your Eyes.” http://www.allaboutvision.com. All About Vision, 2000. Web.9/30/2012.


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