Eli5; Why do halogen lights get burning hot but LEDS don’t get hot at all?
In: Technology
Halogen lights are ordinary incandescent lights, with the wire heating up from resisting the electricity flowing through it, and heating up enough to glow in visible light. The “halogen” means they’re filled with mostly a noble gas plus a little of a halogen compound, and the latter pick sup tungsten that evaporated onto the inside of the container and deposits it back on the filament.
So halogen lights get hot like ordinary oldstyle incandescents did.
LED lights, on the other hand, make light by, basically, running the photoelectric effect backwards, not by heating up to red-hot or yellow-hot to make temperature-based light. They have diodes with an n-type and a p-type semiconductor bordering each other; one has extra electrons flowing through it, and the other has missing electrons, so positively-charged “holes” flow through it the other way under the same current.
At the border, electrons coming one way fall into holes coming the other way, releasing a photon each time. They picked types so that the photon is is the visible-light range. Using three LEDs that give off red, blue, and green light can make an LED light that looks like it’s giving off blended white light. They still give off heat, because they’ve got flowing current, but they don’t base their light-making method off heating up from the current, so they don’t have to make high heat the way incandescent lights do.
–Dave, enlightening, I hope
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