Ultraviolet (UV) light is much like visible light except that it is of higher energy. It occupies that region of the electromagnetic spectrum between visible light and X-Rays.
All forms of electromagnetic radiation can be described in terms of energy, frequency or wavelength (being equivalent). The choice of unit is dependent on the convenience it offers to those working with that radiation.
Ultraviolet (UV) light is typically measured by wavelength in units of nanometres or Angstroms. These are defined as follows;
| Unit (abbreviation) | Metres | Angstroms |
| 1 nanometre (nm) | 1E-09 | 10 |
| 1 Angstrom (Å) | 1E-10 | 1 |
| Region | Wavelengths (Å) |
| X-Rays | 0.1 - 100 |
| UV | 100 - 4000 |
| Visible | 4000 - 7000 |
| Region | Wavelengths (Å) |
| UVA | 3200 - 4000 |
| UVB | 2900 - 3200 |
| UVC | 2000 - 2900 |