Fluorescence & Phosphorescence

Fluorescence and phosphorescence are both examples of photoluminescence. In both cases, light is absorbed and then re-emitted at a less-energetic wavelength. Fluorescent and phosphorescent objects usually glow under exposure to ultraviolet light (though this is not a requirement). Fluorescence involves absorbing and releasing lower energy light almost immediately, while the light release of phosphorescence is delayed, so these materials appear to glow in the dark.