Analytical UV lamps, also called Wood light lamps, generally serve to excite luminescence in substances, by using a wavelength in the UV region to create luminescence in the visible light region. The luminescence is generally divided into fluorescence and phosphorescence. Because of their filtered UV radiation, analytical lamps produce manifestations of luminescence and this has long been used for analytical investigations in all areas of industry and research. Luminescence is understood to be an optical phenomenon, instigated by irradiation with visible light or ultraviolet radiation.