How does a Black Light Work?

A black light works by producing UVA light, or ultraviolet light, that we cannot see. Ultraviolet light is above the spectrum of visible light that our eyes can process. When objects appear to glow under the light, they are substances that are emitting light in response to radiation. These ‘phosphors’ are what make normal things like teeth and white t-shirts glow in the dark! Look here for more information: