Ultraviolet light - (n.)
Also known as UV light, this form of electromagnetic radiation is emitted by the Sun and is invisible to the naked eye. Lying in the electromagnetic spectrum between violet light and X-rays, UV light can be harmful to living organisms, most notably by damaging DNA. UV light comes in three main forms: UV-A, UV-B, and UV-C. UV-C is the shortest and most dangerous wavelength, but it is largely absorbed by the Earth's ozone layer. UV-A, a longer wavelength, usually induces skin tanning in humans, while UV-B, a shorter wavelength, causes sunburns and is most often associated with skin cancer in humans. While the Earth’s ozone layer absorbs about half of the UV-B radiation, UV-A radiation is not absorbed by our atmosphere.