Goggles are sunglasses made to protect eyes.They are used in snow sports, swimming, and you could use them when riding a motocycle.Goggles are worn to protect eyes and prevent flying particles from damaging the eyes.
Goggles are a little different from sunglasses.The are curved to fit the user's face and had a large groove cut in the back to allow for the nose.
Most modern cold-weather goggles have two layers of lens to prevent the interior from becoming "foggy." With only a single lens, the interior water vapor condenses onto the lens because the lens is colder than the vapor. The reasoning behind dual layer lens is that the inner lens will be warm while the outer lens will be cold.
As long as the temperature of the inner lens is close to that of the interior water vapor, the vapor should not condense. However, if water vapor gets between the layers of the lens, condensation can occur between the lenses and is almost impossible to get rid of; thus, properly constructed and maintained dual-layer lenses should be air-tight to prevent water vapor from getting in between the lenses.
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