Hi Peter and everyone,

Materials floresce because some of the chemicals in them absorb the UV light and emit visible light as the aborbed energy is disapated.  Some minerals can be identified this way.  Many biological materials also floresce and some of the chemicals can be identified by this floresce.  It allows an easy way to find certian materials either as contamination or traces left behind.  Food inspectors who are checking the sanitary conditions of a food storage area use UV light to find rodent infestations since dried urine also floresces and can be easily seen under black light.

As for the safety of using UV light - the danger to the eyes depends on the wavelength but since the lights are readily available I don't think there is too much danger with the wavelengths used for this test.

blane



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Blane White
MN Dept of Agriculture
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