fluorescence , luminescence in which light of a visible color is emitted from a substance under stimulation or excitation by light or other forms of electromagnetic radiation or by certain other means. The light is given off only while the stimulation continues; in this the phenomenon differs from phosphorescence , in which light continues to be emitted after the excitation by other radiation has ceased. Fluorescence of certain rocks and other substances had been observed for hundreds of years before its nature was understood. Probably the first to explain it was the British scientist Sir... Read more