ULTRAVIOLET RADIATION

Electromagnetic radiation shorter in wavelength than visible radiation but longer than X-rays; roughly, radiation in the wavelength interval between 10 and 4,000 angstroms. Ultraviolet radiation from the sun is responsible for many complex photochemical reactions characteristic of the upper atmosphere, e.g., formation of the ozone layer through ultraviolet dissociation of oxygen molecules followed by recombination to form ozone.