eli5 Why is lightning purple? As opposed to how electricity usually appears yellow.
In: Physics
It’s more purple or blue or green because of molecules of the air heat up to 30,000K and electrons fall from their atoms. When these atoms fuse back again, light is emitted of a specific wavelength in the spectrum. More Nitrogen atoms will make it more blue, more Oxygen atoms make it more yellow and red. Some other parts of the emitted light are mostly infrared and ultraviolet, so not visible.
Lightning isn’t purple, it’s white. But since it usually appears against dark blue backgrounds, it might seem like it has a bit of a purple aura.
When electricity goes through air it creates ions and releases light. This is called corona discharge.
https://en.wikipedia.org/wiki/Corona_discharge
The purple flavor is from excited N2 (ionized air glow). Nitrogen makes up a large portion of our air.
https://en.wikipedia.org/wiki/Ionized-air_glow
I’ve never seen this as yellow…
Lightning is ionized air. It’s very hot, which gives it a slightly blueish tint white glow. Nitrogen also adds some purple hints to it.
Man made electrical arcs have two components. One, ionized air, excalty like lightning. Will appear a similar colour. This is the arc itself. The second is cooler molten metal, which will glow orange. It’s a colder temperature, so glows an orange white, like a light bulb. The sparks of an electrical arc are molten metal flying off. That’s not the colour of “electricity” (vaguely meaning the colour of whatever path the electricity is following) you are seeing. It’s a side effect of the heat. There is no “electricity” in the yellow sparks. Only in the white lighting like glow of the arc itself. You get the same effect with friction, say banging a hammer on metal or using a metal grinder. It’s just small bits of hot, glowing metal.
Lightning obviously has no metals wires to spark, so no yellow. Though where lightning actually hits something on the ground, it can definitely cause yellow sparks to fly.
Although that’s not to say the white glow of lightning is the colour of electricity. That’s just the colour of hot gas/plasma. Any hot gas will do it, see the sun. There’s no electricity (well, not much relatively), but it glows white. Electricity has no colour, or at least if you wanted to try and claim one it would be be the “colour” radio waves far outside of human vision.
Electricity doesn’t have a color. Electricity is made of electrons, while light is made of photons.
When you “see” electricity, you are actually seeing some side effect of electricity, not the electricity itself. When electricity flows through a gas, it causes the gas to become ionized, and the ionized gas glows. So the color of the ionization is not a function of the electricity, but a function of the gas through which the electricity flows.
Our atmosphere is composed mostly of nitrogen and oxygen. Both of these gases glow blue-white when ionized. If our atmosphere was composed of hydrogen, lightning would be bright yellow. If our atmosphere was neon, lightning would be bright red. If our atmosphere was mercury gas, lightning would be ultra-violet.
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