Invisible electromagnetic radiation with a wavelength of 10-400 nm is called ultraviolet (UV in short).
The phenomenon of ultraviolet radiation was discovered in 1801 by the German physicist Johann Wilhelm Ritter, and independently by the British chemist William Hyde Wollaston.
It is characterized by a wavelength shorter than visible light radiation (400-700nm) and a greater wavelength than X-ray radiation (10 pm-10nm) and gamma radiation (<10pm).
Due to the range of waves, ultraviolet is divided into:
- extreme, 10–121 nm
- far, 122-200 nm
- indirect, 200-300 nm
- close, 300-400 nm
Due to the impact on living organisms, ultraviolet can be divided into:
- UVA 315–380 nm
- UVB 280–315 nm
- UVC 100–280 nm
Sunlight contains all of the above wavelength ranges, but due to the ozone layer of the atmosphere, only UVA radiation with a small amount of UVB radiation reaches the Earth’s surface. Ultraviolet UVC is thus completely absorbed in the ozone layer and therefore does not reach the planet’s surface at all.
As a rule, UV radiation is harmful to living organisms, UVA to a lesser extent, while UVB, and in particular UVC, damages DNA and RNA chains. The first artificial UV light source (UV fluorescent lamp) was created by General Electric as early as 1935.