Black Light Theatre - Optics

Optics

A key principal of Black Light Theatre is the inability of the human eye to distinguish black objects from a black background. This effect results in effective invisibility for any objects not illuminated by the 'black light'. The second optical principal behind Black Light Theatre is the effect of UV light on fluorescent objects. Black lights actually emit as much light as 'normal' lights, but at a frequency that humans cannot detect. While most objects either absorb UV light or reflect it back at the same frequency at which it came in, fluorescent objects absorb UV light then re-emit it a longer wavelength that human eyes can detect. The combined effect is that designers can make some objects appear as bright as if the room were fully lighted, while making other objects appear as dark as if the room were completely dark.