Ultraviolet radiation

Ultraviolet (UV) radiation covers the wavelength range of 100–400 nm, which is a higher frequency and lower wavelength than visible light. UV radiation comes naturally from the sun, but it can also be created by artificial sources used in industry, commerce and recreation.

The UV region covers the wavelength range 100-400 nm and is divided into three bands:

• UVA (315-400 nm)
• UVB (280-315 nm)
• UVC (100-280 nm).

As sunlight passes through the atmosphere, all UVC and approximately 90% of UVB radiation is absorbed by ozone, water vapour, oxygen and carbon dioxide. UVA radiation is less affected by the atmosphere. Therefore, the UV radiation reaching the Earth’s surface is largely composed of UVA with a small UVB component.

The amount of UV radiation from the sun that hits the Earth’s surface depends on several factors, including the sun’s height in the sky, latitude, cloud cover, altitude, the thickness of the ozone layer and ground reflection. Reductions in the ozone layer due to human-created pollution increase the amount of UVA and UVB that reaches the surface. This can impact human health, animals, marine organisms and plant life. In humans, increased UV exposure can cause skin cancers, cataracts and immune system damage.