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Homework Help: Optical Path Length

  1. Mar 8, 2012 #1

    My homework constantly refers to something called the optical path length, L - I'm not exactly sure what this is. It's in the equation below. This question is in relation to astrophysics and dust extinction in the Interstellar Medium.

    Relevant equations:

    Dust optical depth, τλ = Ng∏a2L


    My best guess is that it's something to do with the penetration distance into a cloud(???).

  2. jcsd
  3. Mar 8, 2012 #2


    User Avatar

    Staff: Mentor

    Hmm. Optical depth is something different from optical path length. Optical depth should be related to optical extinction (light absorption by a medium). Optical path length is usually the physical distance of the path that light follows through a system, multiplied by the index of refraction of the medium. L*n in other words.
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