The UV spectrum is divided into three areas:
- UV-A, long wave, 315-400 nm
- UV-B, medium wave, 280-315 nm
- UV-C, short wave,
The radiation from the UV-A group:
is also a part of the natural sunshine on the earth’s surface. This UV-A radiation causes different photochemical processes. It has a perceptible pigmenting – but in praxis no eythematic influence.
The radiations from the UV-B group:
shows both pigmenting and erythematic influence. They also form pre-vitamin D. This kind of radiation is mainly used within therapy.
Short waved UV-C radiation
has a strong germ fatal effect and also causes erythema and conjunctivitis. This kind of radiation can be made artificial, when a mercury low-pressure in UV-C lamps is discharged.
Radiation with wavelengths below 200 nm form ozone.