BACKGROUND

Hazards of UV

Sunlight contains UV radiation, which is a health hazard since it is known that frequent exposure may lead to skin cancer. Small amounts are beneficial since it produces vitamin D in the skin. It is these rays which are responsible for producing a suntan. Prolonged exposure to sunlight is apparently becoming more of a problem due to the depletion of the ozone layer. This layer, high in the atmosphere, absorbs ultraviolet radiation and so reduces the amount which reaches the surface of the Earth. Increasing use of propellants in aerosol spray containers has been stated as the reason why the ozone layer has developed 'holes' through which the rays reach the Earth in large intensities. However, some scientists dispute this: the issue is controversial and research continues to understand the problem more thoroughly. Meanwhile the propellants which have been suggested as responsible, CFCs - chlorofluorocarbons - are being replaced by alternatives which are known not to react with ozone.

Background on UV

Ultraviolet radiation was first detected in 1801 by the German astronomer Johann Ritter using paper soaked in a solution of silver chloride. He noticed that the darkening produced extended beyond the violet end of the visible spectrum, i.e. at shorter wavelengths than visible light.

In the 19th century luminescence was investigated. This phenomenon is the emission of visible light by COLD substances when exposed to radiation of shorter wavelengths. These substances may be used to detect UV radiation.

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