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PGRE | Michelson Interferometer Equation

  1. Feb 27, 2012 #1
    1. The problem statement, all variables and given/known data
    I am having trouble understanding how I would apply the Michelson Interferometer equation to a problem on the PGRE. Here is a link to a diagram displaying the interferometer as well as the equation which is very similar to the way the topic is shown in my REA pgre book.

    2. Relevant equations

    3. The attempt at a solution
    I just don't understand what the variable d is referring to. In the REA book, it says that if the fixed mirror on the right is moved through some distance d, then the number of circular fringes m moves in. And using the aforementioned equation, you can solve for the wavelength of the light. Can anyone explain how this works?
  2. jcsd
  3. Feb 27, 2012 #2


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    d is the change in the distance L; it is how far the movable mirror moves.
    2d is the change in the path the light takes going to the movable mirror and back.
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