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Homework Help: Atmospheric Scattering Problem

  1. Apr 27, 2008 #1
    Hello, just need some guidance - I hope my logic is correct!

    1. The problem statement, all variables and given/known data

    So I have a scenario where the Earth's atmosphere, instead of scattering blue light from the sun, actually scatters green light based on Rayleigh scattering.

    I know that the sky will therefore appear green, but how will the sun appear?

    I reasoned the sun will be magenta using the normal situation on Earth.

    2. Relevant equations

    Not an equation type problem but relies on the Rayleigh scattering principle.

    3. The attempt at a solution

    The sun appears yellow/red (toward sunsets) even though its true color is closer to white because the sun's high frequency light (violet/blue) is scattered in the atmosphere by oxygen and nitrogen molecules. Yellows and reds are low frequency, long wavelength, and are able to penetrate the atmosphere without scattering. During sunsets, the angle of sunlight is very shallow and must go through more atmosphere and undergo more scattering. Much less blue light is transmitted and the low end of the color spectrum is dominant - so we see red/orange sunsets

    If in a similar situation, green light were to be scattered, then wouldn't green light be much less dominant in the color spectrum? So by removing Green from the additive primary colors, we lose yellow (normal perceived sun color) and cyan as well. The blue and red frequency light will be able to penetrate the atmosphere, mix, and result in magenta with a scattered green sky as the background.

    What do you think? I was toying between a yellow or magenta sun....but i think magenta seems a good option.
  2. jcsd
  3. Apr 27, 2008 #2

    Shooting Star

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    If it is Rayleigh scattering, then how come the blue is not being scattered more than the green? I understand the point you are trying to make, but you will have to come up with some different mechanism.
  4. Apr 27, 2008 #3
    Yes, I understand your point. I naturally thought that if the green frequencies were able to be scattered, then the higher frequencies such as blue would be scattered for sure.

    However, the problem does not mention whether scattering is based on just green light or rather the green end of the spectrum all the way up to the higher frequencies. I believe that the question assumes that, given this hypothetical situation, the air molecules act unusually and scatter only the green frequency light. I suppose this situation isn't strictly Rayleigh scattering - sorry.
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