University of Edinburgh

BSL Physics Glossary - ultraviolet radiation - definition

In the electromagnetic spectrum there is an area of visible light. UV radiation has wavelengths shorter than visible light. We can't see it, although birds and insects can. The wavelength of UV light varies from 10-400 nm. Within this UV spectrum there are three different sorts of UV light. The first section, called UVA, has wavelengths of 320-400 nm. The second, UVB, has wavelengths of 290-320 nm. The third, UVC, has wavelengths of 10-290 nm.

A lot of UVA gets through to the Earth's atmosphere. It's good for our skin and bones. A small amount of UVB gets through. This is dangerous radiation which can burn us and give us skin cancer. The atmosphere completely prevents UVC from getting through to the earth.

Ultra-violet light is also fluorescent. For example if a shop wants to check whether a bank note is legal, the note can be placed under a UV light. A genuine note will show a fluorescent pattern.