Ultraviolet radiation itself is invisible to the human eye, but illuminating certain materials with UV radiation prompts the visible effects of fluorescence and phosphorescence. Black-light testing is commonly used to authenticate antiques and banknotes. It is extensively used in non-destructive testing; fluorescing fluids are applied to metal structures and illuminated with a black light, whereby cracks and other artifacts can easily be detected. It can also be used to detect pet excreta for removal, such as urine, vomitus and other substances that are not always visible to the naked eye.

It is also used to illuminate pictures painted with fluorescent colors (preferably on black velvet to intensify the illusion of self-illumination). The fluorescence it prompts from certain textile fibers, especially those bearing optical brightener residue, is also used for its recreational effect (as seen for instance in the opening credits of the James Bond film A View to a Kill).