White light can be made different ways - by mixing reds, greens, and blues, by using an ultraviolet LED to stimulate a white phosphor (the same stuff that's inside a fluorescent bulb) or by using a blue-emitting diode that excites a yellow-emitting phosphor embedded in the epoxy dome. The combination of blue and yellow makes a white-emitting LED. Combine a white phosphor LED with a few amber ones, and you can create a range of different whites - from the romantic glow of a candle flame to the hot, bright light of the sun.
      Most "white" LEDs in production today use a 450nm – 470nm blue GaN (gallium nitride) LED covered by a yellowish phosphor coating usually made of cerium doped yttrium aluminium garnet (YAG:Ce) crystals which have been powdered and bound in a type of viscous adhesive. The LED chip emits blue light, part of which is converted to yellow by the YAG:Ce. The single crystal form of YAG:Ce is actually considered a scintillator rather than a phosphor. Since yellow light stimulates the red and green receptors of the eye, the resulting mix of blue and yellow light gives the appearance of white.
      White LEDs can also be made by coating near ultraviolet (NUV) emitting LEDs with a mixture of high efficiency europium based red and blue emitting phosphors plus green emitting copper and aluminium doped zinc sulfide (ZnS:Cu,Al).

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