Ultra Violet radiation was discovered in 1801, because of it's effect on photographic plates. The wavelength range of Ultra Violet is 4000 to 10 Ångström (Å=10^-10m) . Ultra Violet radiation causes the skin to brown, or to burn, when an overdose of radiation is applied. They produce vitamin D in the human body, which is essential for a good health.

Ultra Violet light from the sun Created by the SOHO satellite

The sun is a strong emitter of UV radiation, but fortunately for us, the Earth's atmosphere shields its inhabitants from the sun's harmful UV light. In the upper atmosphere lies the ozone layer, where most of the UV radiation is absorbed. This region of O₃ is created by the interaction of UV photons with molecular oxygen, O₂. The ozone then absorbs other UV photons, re-emitting them as infrared photons, and heat. So the ultraviolet photons can not only harm us in burning our skin and causing other skin maladies, but can also help us in that it helps create the atmospheric layer that then blocks out other UV photons. Small amounts of UV can create the ozone layer but when the ozone layer is created it can block large amounts of UV.

Ultra Violet radiation, which has a wavelength smaller than 3000 Ångström are the most dangerous, they can damage the eye, or even destroy plants. However, the ozonlayer of the earth absorbs most of the radiation with such a small wavelength. Glass has a similar effect.

Some materials become fluorescent when exposed to this type of radiation, but only as long as it's exposed to it. Sometimes these materials are used in commercial purposes, because they become shiny in the daylight. For example the white color of some detergent is caused by these materials.

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