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The wavelength (100-400 nanometers) of UV rays is shorter than visible light and cannot be seen by humans. However, not all ultraviolet rays emitted from the Sun reach the earth. Ultraviolet rays (UVC) in the range of 100-280 nanometers in the wavelength are completely absorbed by the atmosphere, while a small portion of the ultraviolet rays (UVB) in the range of 280-315 nanometers and UVA rays (ultraviolet rays in wavelength greater than 315 nanometers) reach the earth. Studies show that UVA and UVB rays cause premature skin aging, skin cancer, and eye damage (such as cataracts).
Sunglasses used to protect the eye from the harmful effects of sun rays should block almost all (99-100%) of ultraviolet rays to provide effective protection. For this, eyeglass glasses or coatings that are capable of blocking UV light are generally used. In addition, tinted glasses used in sunglasses absorb light of certain wavelengths and prevent these rays from reaching the eyes.