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as far as the practical use mabey u could look on the back of ur pc for a bug sitten over your nic or your routers led.
I wouldnt doubt some kind of tech is available to utilize this I have seen...

sorry about that I will remember that in the future.
I just wanted to get everything.
If u would like i will shorten it.

source:http://applied-math.org/optical_tempest.pdf
now this article is very extensive and legnthy
just to warn you
I have cut the article and there is alot of tech jargon missing but feel free to...