The really simple explanation: A light emitting diode is a solar cell
working in reverse.
Why they are colored: This "bandgap energy" business about
semiconductors. The light they put out is of wavelength close to or maybe
somewhat longer than the longest wavelengths at which they can work as a
If you put an LED on a microammeter and have sunlight hit the LED,
youmay get a reading. You will not get much, and one reason is that the
ship is so small that only a tiny amount of sunlight will be collected by
I believe regular solar cells will put out a bit of infrared if you push
a DC current through them in reverse.
- Don Klipstein ( firstname.lastname@example.org)
Electrons, mumble mumble, quantum energy levels, mumble mumble, state
Contrary to comments that LEDs require DC, I think you'll find that the
cheapo Xmas lights work on AC, and simply flash on an off as the
voltage alternates. You can prove this by waving a bulb rapidly in
front of your face and seeing multiple discrete images. (Unlike
incandescent filaments, LEDs turn on and off almost instantly, so the
light doesn't ride through the AC voltage cycle.)
Mebbe they rectify the AC and give you 120 Hz, or maybe they don't so
you get 60 Hz. A DC power supply to provide constant light would negate
the cost savings and reliability of the simple solution.
Light is just an atom's way of screaming.
When you pump electricity through a fillament, it
gets really hot, and the atoms start screaming.
The chemicals burried in the middle of a diode
are just a lot more excitable than tungsten atoms,
so they get all excited by just an electric shock.
All atoms have bands of electrons circling the nucleus. When you excite
these electrons, by heat or by electricity, the electrons jump to the
outer bands. It takes energy to do this. When the electrons return to
their normal band they shed that energy in the form of photons (i.e.
light) The difference in bulbs and LED's is the energy source to get
the electrons to move. Bulbs require heat. LED's are made of atoms
that easily get the electrons to move with low voltages.
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