How to see UV light?

Question

HI, I have a pond filter that uses UV light to kill bacteria but since UV light is invisible, I cant tell if it is on or now. Does anyone know of something that I could use to be able to see the UV light?

Answer 1

Humans can't see UV light, but some birds can. But when you expose a fluorescent material to UV light, it absorbs the UV and emits light at a longer wavelength, in the human visible spectrum. Try anything that glows in black light. Many white shirts will. But the filter might be designed so that the UV light doesn't leave the filter. If you can't see the bulb from the outside, then you might not be able to detect the light.