To summarise: Fluorescence is a physical property whereby light of one wavelength is converted to another usually longer wavelength. The conversion is virtually instantaneous and is difficult to to discern by eye especially if blue or ultraviolet excitation is required. The effect only persists after the excitation source is extinguished. The effect is called phosphorescence.
Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors.
