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Does an electrical spark / arc cast a shadow? For example, if you shine a flashlight through the sparks generated through a tazer, will it cast a shadow on the wall? Unfortunately I don't have a tazer handy to conduct my own experiment here. I know from google searches that fire does not cast (much of) a shadow, but have not been able to find out how light passes through sparks yet.

Edit: This is a bit different than fire (here, talking about an electrical arc or spark vs. fire, which may or may not behave the same).

Jonathan
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  • @Sammy gerbil This is not a dupe of that question, here I am asking about sparks vs. fire. I did not see sparks discussed in any of the answers to that question. – Jonathan Jul 29 '17 at 14:13
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    Both sparks and flames are made up of ionized gases which are otherwise invisible. – sammy gerbil Jul 29 '17 at 14:28
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    That's not an exact duplicate of the flame one. But, indeed, the spark discharge propagates through a plasma-like channel that is not much unlike that of a flame, the big difference being that in a spark there are only atmospheric gases. The main mechanisms for casting a shadow are 1) reflection, 2) refraction (depending on the definition of shadow), and 3) absorption: (1) is negligible and similar to air - no shadow; (2) if it counts, a bit stronger than with flames (higher temp.); (3) with no fuel related gases, I'd expect the absorption to be weaker. My bet? Even less shadow than flames. – stafusa Jul 30 '17 at 02:50
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    A spark is an avalanche discharge; it contains free electrons, so it's a LOT different from a flame, which contains more-massive ions. The free electrons may result in metal-like light blockage, for visible light below the plasma frequency. – Whit3rd Jul 30 '17 at 09:20
  • May have to borrow a tazer from someone and use a flashlight to answer this :-) Appreciate the responses so far! – Jonathan Aug 01 '17 at 16:37
  • Well, I tried the experiment, and as far as I can tell, a spark does not cast a shadow / block light. It was pretty easy to verify with a tazer and a flashlight, shine the flashlight through the tazer to the wall. However, one thought is if the spark is really pulsating (e.g. the spark is only there 1/100th of the time for example), it may be that it does cast a shadow, but it is too weak to identify. – Jonathan Jan 02 '18 at 21:43

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