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U

Ultraviolet (UV) Radiation Radiation in the electromagnetic spectrum from wavelengths of 100 to 3900 A. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that individuals can identify as the color violet. UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. It is considered a danger to eyes and overexposure to the skin causes severe skin burns. UVA includes the wavelengths from 313 to 400 A, and UVB covers the wavelengths from 280 to 315 A. Both UVA and UVB destroy vitamin A in skin, which may cause further damage. UVA is also known to contribute to skin cancer via indirect DNA damage. UVC rays are the highest energy, most dangerous type of ultraviolet light. UVC rays are filtered out by the atmosphere.