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I'm not well-versed in physics, so I hope you'll forgive me if this question is significantly off the mark.

I'm interested in the predominant frequencies of light over the course of one day. My understanding is that as the sun rises and falls, the atmosphere absorbs differing amounts of light, and that is responsible for the changing colour of the daylight, for example becoming more red as the sun sets.

I guess that there is some curve from (all but) absolute darkness, through to broadband white light during the middle of the day, back to darkness again over the course of twenty-four hours?

If so, is it possible to approximate the makeup of the light at a given point during the day? And if so, how? I appreciate that there are probably significant complicating factors, so any rough approximation would be fine.

Again, I'm coming from a layman position here, so I apologise if I've drastically misunderstood something.

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    $\begingroup$ Just to check: Are you only interested in visible light? Also: When you say "predominant" you're referring to the total intensity accumulated during 24 hours right? Furthermore, it will depend on your latitude and day of the year. $\endgroup$ – cinico Nov 27 '13 at 18:03
  • $\begingroup$ @cinico: I'm particularly interested in visible light, but my question is kind of exploratory so any information would be appreciated. What I meant by predominant is that at a particular point in time, what is the makeup of the light in terms of what frequencies are present; so for example in the morning and evening I'd expect a bias towards the red end of the visible spectrum, and a wider set of frequencies (i.e. a whiter light) towards the middle of the day. $\endgroup$ – kfb Nov 27 '13 at 22:05
  • $\begingroup$ @kfb I think cincio is trying to imply that when you get to IR pretty much everything on the planet will be glowing $\endgroup$ – jk. Nov 28 '13 at 14:40
  • $\begingroup$ @jk. Ah, I see. In that case, I think sticking with visible light makes sense for what I'm currently thinking of. $\endgroup$ – kfb Nov 29 '13 at 10:48
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I found a good paper that can help you. However, due to copyright issues I cannot put the spectra here.

Try to get this article:

"The Distribution of Energy in the Visible Spectrum of Daylight". A. H. TAYLOR and G. P. KERR. J. Opt. Soc. Am. 31 no. 1, pp. 3-8 (1941) . Also available here (pdf).

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  • $\begingroup$ 1941 copyright... is it still considered to be under copyright? Do the copyright law corruptions created for one Mickey Mouse corporation (Disney) by their wholly owned subsidiary (the US Congress) also apply to scientific papers? $\endgroup$ – Phil Perry Jun 23 '14 at 17:06

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