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Ultraviolet (UV) is part of the spectrum of electromagnetic radiation being emitted by the sun that arrives at the edge of the Earth’s atmosphere. The sun is extremely hot so it emits a large amount of radiation at short wavelengths, below the visible band. However, the atmosphere greatly affects the spectrum of the radiation that reaches the surface.

The section ‘What is UV’ describes the different wavebands of ultraviolet radiation emitted by the sun, UVA, UVB and UVC, and how the earth’s atmosphere determines the intensity and spectrum of the UV reaching the surface. It also introduces the concept of UVE, the ‘Erythemally active UV irradiance’ that effects human skin, and the Global Solar UV Index (UVI).

The section on the ‘Effects of UV radiation’ explains in detail the Global Solar UV Index and the effects of UV on the human population. It also covers the effects of changes in UV irradiance on the wider biosphere and ecosystems; such as crops, forests, freshwater and marine life. UV also has considerable effects on the degradation of materials, particularly plastics, which become embrittled and discoloured.

How to measure UV radiation’ gives an overview of the types of instruments most commonly used. The Brewer MkIII Spectrophotometer can make high quality spectral scans of the ultraviolet radiation from the sun or sky to derive UVA, UVB, UVC and UVE/UVI.