Whats the shining range of a regular fluorescent black light?
The range of any light is infinite! So your question is really about how bright you want it to be because light spreads out as it travels further. Using reflectors or lenses to focus the light makes it spread less so you can get high intensity further from the light. Lenses aren’t so good with UV light, so try to get a good reflector. You should get a good response at 3m, although obviously it depends how strong your light source is. Have you thought about UV torches? They are all ready built to produce a narrow beam of light that produces good results several metres away.
