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

See e.g. http://en.wikipedia.org/wiki/Radio_spectrum#By_frequency

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
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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
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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
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-1 well this is completely wrong –  Larry Harson Jul 23 '12 at 16:16
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@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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