ULTRAVIOLET (UV)

Electromagnetic radiation with wavelengths between that of visible violet light and X-rays; it ranges from 400 to 4 nanometers. Ultraviolet is subdivided into near (NUV) 400 to 300 nanometers, far (FUV) 300 to 200 nanometers, extreme (XUV) 200 to 100 nanometers, and vacuum (VUV) 100 to 4 nanometers. Most of the potentially hazardous UV radiation emitted by the Sun is absorbed by the ozone layer. [See also radiation.] updraft A rising air current.