Subtypes
The electromagnetic spectrum of ultraviolet light can be subdivided in a number of ways. The ISO standard on determining solar irradiances (ISO-21348) describes the following ranges:
| Name | Abbreviation | Wavelength range (in nanometres) |
Energy per photon (in electronvolts) |
Notes / alternative names |
|---|---|---|---|---|
| Ultraviolet | UV | 400 – 100 nm | 3.10 – 12.4 eV | |
| Ultraviolet A | UVA | 400 – 315 nm | 3.10 – 3.94 eV | long wave, black light |
| Ultraviolet B | UVB | 315 – 280 nm | 3.94 – 4.43 eV | medium wave |
| Ultraviolet C | UVC | 280 – 100 nm | 4.43 – 12.4 eV | short wave, germicidal |
| Near Ultraviolet | NUV | 400 – 300 nm | 3.10 – 4.13 eV | visible to birds, insects and fish |
| Middle Ultraviolet | MUV | 300 – 200 nm | 4.13 – 6.20 eV | |
| Far Ultraviolet | FUV | 200 – 122 nm | 6.20 – 10.16 eV | |
| Hydrogen Lyman-alpha | H Lyman-α | 122 – 121 nm | 10.16– 10.25 eV | |
| Extreme Ultraviolet | EUV | 121 – 10 nm | 10.25 – 124 eV | |
| Vacuum Ultraviolet | VUV | 200 – 10 nm | 6.20 – 124 eV |
Vacuum UV is so-named because it is absorbed strongly by air, and is therefore used in a vacuum. In the long-wave limit of this region, roughly 150 – 200 nm, the principal absorber is the oxygen in air. Work in this region can be performed in an oxygen-free atmosphere (commonly pure nitrogen), avoiding the need for a vacuum chamber.
Read more about this topic: Ultraviolet