|MadSci Network: Chemistry|
The "black light" is a light which illuminates the area with ultraviolet radiation or uv light. Substances that appear in this light exhibit fluorescence and are emitting light at a higher wavelength and appear to "glow" in the dark. Urine is one substance that can be detected by a uv light but there are many other substances that can fluoresce including saliva, semen, perspiration, household cleaners, etc. The uv light aids in locating a stain but further testing must then be performed upon the stained area to confirm the identity of the substance. Dale L. Laux
Try the links in the MadSci Library for more information on Chemistry.