False-color image of the Sun’s corona as seen in deep ultraviolet by the Extreme ultraviolet Imaging Telescope
Black light fluorescent tubes, a common source of long wave (UVA) ultraviolet.Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3eV to 124 eV. It is named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.
Although ultraviolet is invisible to the human eye, most people are aware of the effects of UV through the painful condition of sunburn, but the UV spectrum has many other effects, both beneficial and damaging, to human health.
UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. It can cause chemical reactions, and causes many substances to glow or fluoresce. Most ultraviolet is classified as non-ionizing radiation. The higher energies of the ultraviolet spectrum from about 150 nm (‘vacuum’ ultraviolet) are ionizing, but this type of ultraviolet is not very penetrating and is blocked by air.