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Long vs Short light wavelength absorption

  1. Jul 25, 2012 #1
    Hi all

    I was reading through an astrophysics book{1} and there I came across this sentence:

    " A dust cloud can either scatter or absorb light that passes through it. Since shorter wavelengths are affected more significantly than longer ones, a star lying behind the cloud appears reddened to an observer."

    I do not understand why shorter wavelengths are affected more than longer wavelengths. I may be missing some basic relation but I can't figure it out right now.


    {1}: "An introduction to modern astrophysics", R. W. Carroll, D. A. Ostlie, page 439
  2. jcsd
  3. Jul 25, 2012 #2
    hmm...I think it would be sth like this:

    shorter wavelength -> higher energy particles -> more collision with dust cloud particles

    is that correct?
  4. Jul 25, 2012 #3
    well i found the answer before anybody answers me, i thought i should post it for future ref

    same book, page 440 explains in detail about how shorter wavelength can be greater affected by the environment than long wavelengths.

    As an example, the large ripples on a pond can travel along without being disturbed by the leafs and dust grains on the surface of the pond whereas small ripples get distorted.

    I hope this post will be useful for someone in future.
  5. Jul 25, 2012 #4


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    2017 Award

    Staff: Mentor

    To add a wikipedia link: Rayleigh scattering
    The same mechanism is responsible for our blue sky.
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