For general lighting, what people need is mainly a white light source. In 1998, white LEDs were successfully developed. This LED is made by encapsulating a GaN chip and yttrium aluminum garnet (YAG). The GaN chip emits blue light (λp=465 nm, Wd=30 nm), and the Ce3+-containing YAG phosphor prepared by high-temperature sintering is excited by the blue light to emit yellow light with a peak of 550 nm. The blue LED substrate is mounted in a bowl-shaped reflective cavity covered with a thin layer of resin mixed with YAG, about 200-500 nm. The blue portion of the LED substrate is absorbed by the phosphor, and the other portion of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light. Now, for InGaN/YAG white LEDs, by changing the chemical composition of the YAG phosphor and adjusting the thickness of the phosphor layer, white light of various colors having a color temperature of 3500 to 10000K can be obtained.
White light is composed of various colors of light. Normal sunlight and fluorescent lamps belong to white light.
White light is light composed of visible light (red orange yellow green blue blue purple) and invisible light (microwave radio wave infrared ultraviolet X-ray r-ray, etc.).
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