As far as I understand, you need to be able to mix red, green and blue light to get white light and replace lightbulbs. But the earliest example I can find of white LEDs used a blue LED and a yellow (apparently the result of mixing red and green light) phosphor coating to scatter the light across the visible spectrum. Why couldn’t something similar be done with a red LED and a cyan (mixing blue and green) coating/cover to produce white light instead?
In: Engineering
Blue is special because it is the highest frequency of visible light and has the most energy per photon. You can remove energy by absorbing and re-radiating but you can’t add energy the same way. Hence, you can use phophors to turn blue into other colors but you can’t use the same method to go “uphill” and turn other visible colors into blue.
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