Climbers equipped, both professional symbol, it is for safety. They are equipped with all the equipment in the middle, without exception, there will be a pair of sunglasses. This is not to be cool, which is mainly to protect the eyes.
Mountain air is very thin, to 8,000 meters of altitude, the air is only about one-third of the ground. On this planet we live, towering 14 independent peak altitude of over 8000 meters, in which the most well known is Mount Everest. In addition, on the mountain sun radiation is particularly strong, due to the clean mountain air, very little dust, radiation from the sun and therefore not hindered. Another outstanding problem is generally more than 5000 meters high peaks, have accumulated a thousand years of snow. White stuff, particularly strong ability to reflect light. On a bare peaks, the snow will be more intense reflection of sunlight entering the eyes.
Sunlight contains various wavelengths of light: infrared, red, orange, yellow, green, blue, indigo, violet, ultraviolet, near the red light contains a larger proportion of thermal energy, violet contained small proportion of thermal energy. Since the mountains especially strong solar radiation, ultraviolet and infrared increases. Human eyes are the most sensitive light-sensitive organs, strong ultraviolet and infrared radiation on the eye, can cause radiation damage to eyes. Infrared eye injury which is mainly thermal effects, can cause ultraviolet radiation on the cornea and conjunctiva epithelial damage caused by inflammation caused by what we call snow blindness, manifested as severe foreign body sensation, irritation, photophobia, lacrimation and open eyes, eyelid swelling, conjunctival edema, blurred vision and the appearance of the situation.
So people climb mountains, in order to protect the eyes, must wear a pair of special sunglasses. This is not an ordinary sunglasses lens glass, but the glass was added in the ability to absorb infrared and ultraviolet iron oxide and cobalt oxide. After these two chemicals mixed together, made of black glass.
(The answer from tadpoles finishing staves)
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