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Homework Help: Intensity of Double Slit Pattern

  1. May 3, 2009 #1
    1. The problem statement, all variables and given/known data
    Could anyone help me to explain how the intensity of the double Slit pattern works because i'm looking at the formula and i'm really confused...

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 3, 2009 #2


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    Homework Helper
    Gold Member

    What specifically do you want explained? The formula is easy to derive geometrically using the phasor diagram. Or you can do it algebraically: since only the phase difference matters, let the complex amplitude from slit one be just A (a real number). Then the complex amplitude from slit two will be Ae. The sum is therefore A(1 + e) = A(1 + cosφ + isinφ), and the magnitude squared is A²(1 + cos²φ + 2cosφ + sin²φ) = A²(2 + 2cosφ) = 2A²(2cos²(φ/2)) = 4A²cos²(φ/2).
    Last edited: May 3, 2009
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