Portion of the electromagnetic spectrum extending from the violet end of visible light to the X-ray region.
Ultraviolet (UV) radiation lies between wavelengths of about 400 nanometres and 10 nanometres, corresponding to frequencies of 7.5/n 00D7; /n10 14 Hz to 3 00D7; 10 16 Hz. Most UV rays from the Sun are absorbed by the Earth's ozone layer . UV has low penetrating power, so its effects on humans are limited to the skin. These effects include stimulation of production of vitamin D , sunburn , suntan, aging signs, and carcinogenic changes. UV radiation is also used to treat jaundice in newborns, to sterilize equipment, and to produce artificial light.