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Size does matter? Rayleigh scattering question

  1. Dec 3, 2008 #1
    Why must the size of the particles be much smaller than the wavelength (of say blue light) in Rayleigh scattering? They type that causes the sky to be blue specificly.

    In Short: How does a small electromagnetic wave size up the size of the entire particle before deciding how it will interact with the electric charges within which are all the same?

    In Long: The way I understand it, electrical charges in the molecules will move in an electric field causing the scattering (or remitting the light but with more power in the blue). So if you had a huge particle made of say Nitrogen molecules (say a Nitrogen Ice Cube if such a thing exists) which cause blue light to be scattered then you would experience the same effect with a huge particle.

    And since all molecules have the same electric charges in them (the electron) shouldn't all meterials cause Rayleigh scattering? That would make everything look blue.
  2. jcsd
  3. Dec 4, 2008 #2
    Try Wikipedia:

    Rayleigh scattering is based on a mathematical approximation (simplification) where particles are much smaller than the wavelength of the impinging light. If that approximation doesnt hold, scattering still happens...but the math is different ....more complex

    See Mie Theory, the general solution to Maxwell's equations:

    Better to think of scattering in general and Rayleigh as a special case...
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