Definition: Physical phenomenon in which energy of one wavelength is absorbed by a substance which then emits light of different (usually longer) wavelength: e.g. ultraviolet light is absorbed and visible light is emitted. * Effect ends very quickly after incident light is removed. * A form of luminescence. * Used in microscopy and ophthalmology: fluorescent substance e.g. fluorescein absorbed differentially by certain tissues or parts of cell. When illuminated with e.g. UV radiation, only parts which have absorbed fluorescein will be visible.* Used also in optical brightners to improve apparent whites of black & white prints.

Related Terms: allochromy, phosphor

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