FLUORESCENCE

The phenomenon of fluorescence is a process in which an atom absorbs energy, typically light at a certain wavelength, and then immediately (or within a few nanoseconds) re-emits light at a different wavelength. It is a form of photoluminescence that is faster and more intense than phosphorescence. Fluorescence is used for nighttime visibility of dials and hands (e.g., Super-LumiNova). Such substances have permanently replaced radioluminescent materials, such as radium and later tritium (both radioactive).