Our sun is the source most of the ultraviolet light (UV) that you are likely to come in contact with. UV is not part of the visible light spectrum because it has a shorter wavelength. It gets its name from the fact that it is closer to the part of the visible light spectrum where we perceive the color violet. Other sources of UV light are older computer monitors, fluorescent lights, high-intensity mercury vapor lamps, xenon arc lamps, and even a welder’s flash.
UV light is generally divided into three types: UVA, UVB, and UVC. Virtually all of the UVC is blocked by the ozone layer in the upper atmosphere of the Earth along with some of the UVA and UVB. UVB is important to human health because when our skin is exposed to UVB it induces the production of vitamin D. However, too much exposure causes sunburn, DNA damage, and skin cancer.
Our eyes can also be damaged by exposure to UV light:
UVB is absorbed by the cornea of the eye. Too much exposure can lead to pterygia (a non-cancerous growth of the clear, thin tissue that lays over the white part of the eye), pingueculae (yellowish, slightly raised lesions that form on the surface of the white part of the eye), and photokeratitis (a burn of the cornea).
UVA is the most damaging to the eye because it is not absorbed by the cornea, instead it affects the lens of the eye. Adverse effects include photochemical eye damage and cataracts.
What can you do to protect yourself? Wear appropriate eyewear that is treated to block UV radiation.