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Average UV at noon 1996-2002 (European Space Agency) The ultraviolet index, or UV index, is an international standard measurement of the strength of the sunburn-producing ultraviolet (UV) radiation at a particular place and time. It is primarily used in daily and hourly forecasts aimed at the general public.
Many people who suffer from psoriasis or other skin diseases have their own UV-B lamp at home. A small lamp is used to treat small areas of the skin, while full body cabins treat the whole body, mainly at clinics and hospitals. Overexposure to UV-B light can burn the skin, so the exposure time must be regulated by a timer that turns off the lamp.
Like all fluorescent lamps, the low-pressure lamps will burn for a long period of time. They will, however, lose their ability to produce a reasonable amount of UV after a short while. Typical lifespans for low-pressure lamps are from 300 to 1,600 hours of actual use although they may light and produce very little UV for as much as 5000 hours.
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The WHO-standard ultraviolet index is a widely publicized measurement of total strength of UV wavelengths that cause sunburn on human skin, by weighting UV exposure for action spectrum effects at a given time and location. This standard shows that most sunburn happens due to UV at wavelengths near the boundary of the UVA and UVB bands.
UV source intensity is sometimes specified as irradiance at a distance of 1 meter, which can be easily converted to radiant intensity. UV intensity is inversely proportional to the square of the distance so it decreases at longer distances. Alternatively, it rapidly increases at distances shorter than 1 m. In the above formula, the UV intensity ...
This is similar to the situation in a hydrogen flame. Arc lamps made with ordinary light-hydrogen provide a very similar UV spectrum to deuterium, and have been used in UV spectroscopes. However, lamps using deuterium have a longer life span and an emissivity (intensity) at the far end of their UV range which is three to five times that of an ...