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05 What is "UV-B"?




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This article is from the Ozone Depletion: UV Radiation and its Effects FAQ, by Robert Parson rparson@spot.colorado.edu with numerous contributions by others.

05 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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