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What is the history behind the factors of 3 in the classification of electromagnetic radiation?

See e.g.

Is this (just) inherited from the meter unit via the wavelenght frequency dependence or light?

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most likely yes – Arnold Neumaier Jul 23 '12 at 14:35

2 Answers 2

up vote 4 down vote accepted

Most likely, the 3 is an approximation to 2.99792458 (the number of meters light travels in 10 nanoseconds), as the boundaries of the wavelength perfectly fit the metric scheme.

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+1 And this is completely right – Larry Harson Jul 23 '12 at 16:16
@LarryHarson: I agree, but you should be aware of the sqrt(10) business does fit with half-way logs. It's a coincidence of the speed of light in this case, but perhaps not elsewhere. – Ron Maimon Jul 23 '12 at 18:42

I believe it's just an approximation to 3.1623 (the square root of 10) which is what happens if you make a log-bin in base 10 and split it into regions which include powers of 10 with the most padding, so that you divide the log-region into 1.5-5.5, so that you are 100% sure where all the integer powers of 10, 1,2,3,4,5 go.

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It is far more likely to be just an approximation to 299,792,458 (the number of meters light travels in a second), as the boundaries of the wavelength perfectly fit the metric scheme. – Arnold Neumaier Jul 23 '12 at 14:37
@ArnoldNeumaier: Oh, maybe! That's a better answer--- why don't you post it. – Ron Maimon Jul 23 '12 at 14:51
-1 well this is completely wrong – Larry Harson Jul 23 '12 at 16:16
@LarryHarson: I agree, and it is good that you point it out. I would downvote my answer, but I can't. I don't want to delete it, because although it is wrong, I think it adds something to this question (although it's not that deep a question). – Ron Maimon Jul 24 '12 at 1:41

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