A thorough expaination of how sunglasses work. Discussion of mainly 4 areas: Intensity Reduction, Thin-film Technology, UV Absorption and Polarization.

Essay by little-zHigh School, 11th grade August 2006

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Sunglasses- Purpose and Design

Sunglasses are becoming more and more popular these days. When picking a pair of sunglasses, the ones which have cool looking and famous brands are the most attracting ones to consumers. People tend to forget the real functions one pair of sunglasses can provide. A good pair of sunglasses should have these qualities:

1. Provide protection from ultraviolet rays in sunlight. Good sunglasses can eliminate UV rays completely.

2. Provide protection from intense light.

3. Sunglasses provide protection from glare. Good sunglasses can completely eliminate glare using polarization.

4. Sunglasses eliminate specific frequencies of light. Certain frequencies of light can blur vision, and others can enhance contrast. Choosing the right color for your sunglasses lets them work better in specific situations.

Intensity Reduction

The brightness or intensity of light is measured in lumens. For example, when you are indoors, most artificial light is around 400 to 600 lumens.

If you go outside on a sunny day, the brightness ranges from about 1,000 lumens in the shade to more than 6,000 lumens on a large stretch of concrete, like a highway. Our eyes are comfortable until we get to around 3,500 lumens. When the brightness of the direct or reflected light gets to about 4,000 lumens, our eyes begin to have difficulty absorbing the light. What we see when we try to look at these brighter areas are flashes of white -- this is glare. To reduce the discomfort caused by the amount of light entering our eyes, we squint. Once you get to around 10,000 lumens, your eyes are so bombarded that they begin to completely block out the light. Prolonged exposure to light of such intensity can cause damage resulting in temporary or even permanent blindness. Normally, a good pair of sunglasses adopts two ways...