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 × 1014 Hz to 3 × 1016 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.
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It was performed live on the Zoo TV Tour for the first four legs, usually as the second song in the encore. During these encores, Bono was dressed as either the Mirror Ball Man (first three legs) or Mr. MacPhisto (Zooropa leg), his alter-egos. The song typically followed a phone call by the character performing that night.
It was during the writing of this song that the hit single, "One", came about. Trying to write the bridge to "Ultraviolet", The Edge improvised a riff that the rest of the band rallied around. It was out of this that "One", which changed the outlook of recording sessions for the album, was born. The riff can also be heard on the B-side "Lady with the Spinning Head".
The song is featured in the 2007 film The Diving Bell and the Butterfly.