Phosphors And Color
The phosphor converts the UV output from the mercury discharge into visible light via fluorescence. The mix of color emitted depends on the chemical compounds used in the phosphor. Many compounds produce what is perceived as a white light, which may indeed be a broad emission centered around 590 nm, as in the case of the so-called cool white and warm white halophosphates (the warm contains more red than the cool). However, recent developments in phosphors for television tubes have resulted in the introduction of the "triphosphor," which is a mixture of three different phosphor components emitting in the blue, green, and red. The light from a triphosphor tube distorts an object's perceived color less than that of a halophosphate tube, and changing the mix of the three components allows the lighting engineer to adapt the output of the lamp to suit certain specific purposes, for instance to better match the lighting within a building to the activities of its occupants.
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