For alternative meanings, see ultraviolet (disambiguation). "uv" redirects here. for other uses, see uv (disambiguation). ultraviolet (uv) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, that is, in the range 10 nm to 400 nm, corresponding to photon energies from 3 ev to 124 ev. it is so-named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet.