| Themes > Science > Earth Sciences > Hydrology, Meteorology, Climatology > Meteorology / Climatology > The Ozone Layer > UV Radiation and its Effects > What is "UV-B"? |
"UV-B" refers to UV light having a wavelength between 280 and 320 nm. These wavelengths are on the lower edge of ozone's UV absorption band, in the so-called "Huggins bands". They are absorbed by ozone, but less efficiently than shorter wavelengths ("UV-C"). (The absorption cross-section of ozone increases by more than 2 orders of magnitude between 320 nm and the peak value at ~250 nm.) Depletion of the ozone layer would first of all result in increased UV-B. In principle UV-C would also increase, but it is absorbed so efficiently that a very large depletion would have to take place in order for significant amounts to reach the earth's surface. UV-B and UV-C are absorbed by DNA and other biological macromolecules, inducing photochemical reactions. UV radiation with a wavelength longer than 320 nm is called "UV-A". It is not absorbed by ozone, but it is not usually thought to be especially dangerous. (See, however, question #6.) For a good introduction to many aspects of UV and UV measurements, see the web page for Biospherical Instruments: http://www.biospherical.com/research/uvhome.htm |
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