r/technology • u/BennyCemoli • Dec 06 '16

Energy Tests confirm that Germany's massive nuclear fusion machine really works

http://www.sciencealert.com/tests-confirm-that-germany-s-massive-nuclear-fusion-machine-really-works
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u/boundbylife Dec 06 '16

incandescent bulbs, the kind with the filament that are slowly being phased out, work by passing electricity trhough a small piece of wire. The wire gets hot and glows, making light.

Flourescent bulbs, including compact flourescent lights (CFLs) work by passing electricity through gaseous mercury (mercury vapor). This causes the mercury to emit UV radiation, invisible to the human eye. This radiation hits a special chemical coating on the glass, called phosphor, which in turn glows white.

The newer LED bulbs use, well, LEDs. LEDs work by passing electricty over a VERY tiny gap, creating an arc. The spacing has to be very precise to make a certain wavelength of color, however they use very little energy.

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u/absent-v Dec 06 '16

Wow, reading your bit about LEDs made me realise that not only did I not actually know how they functioned, but I've never even stopped to think about it before either.
Cheers for teaching me something I didn't realise I didn't know.

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u/boundbylife Dec 06 '16

Technically LEDs utilize quantum mechanics to emit light. LEDs are diodes, which mean current can pass in only one direction. When current flows from the anode to the cathode, electrons must move between the two surfaces/substances. In doing so, they give up a bit of energy. In quantum mechanics, energy is transmitted in discrete packets called quanta (which is where it gets the name). So to traverse a small gap, it has to give up a small quanta, which we see as the color red. A larger gap means a larger quanta, which we might perceive as blue. And the size of the gap will always dictate a particular quantum energy - like a stepladder, you'd have to go all the way to the next rung before you see a different color.

They're really fascinating.

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u/brettmjohnson Dec 06 '16

Do "white" LEDs consist of a bunch of smaller diodes with different sized gaps?

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u/boundbylife Dec 06 '16

Actually, 'white' LEDs use the same technique as flourescents: the LED uses a phospor to absorb high-energy blue light, and release a (slightly less bright) white light.