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Homework Help: Light being intercepted by dust

  1. Feb 15, 2006 #1
    There exists one dust grain of radius 0.1 micrometer per every 10^12 hydrogen atoms. Show that as light travels through a 1 cm layer of this comrpessed gas, only about 1% will be intercepted.

    Then show how thick a layer would be needed to block 1/e of the rays.

    I believe the density of the gas is about 2.7 x 10^19 atoms cm^-3

    Initially I thought that I should have used mean free path to solve this problem, but it was done with integrals. I'm assuming that this is an expected value problem, but I really have no idea how to set up the integrals. I believe that my variable must be the thickness of the gas however. Any hints?
  2. jcsd
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