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Light interference homework

  1. Jun 9, 2006 #1
    the question is A plane wave of 400-nm light is incident on a 25-µm slit in a screen, as shown in the figure below. At what incident angle will the first null of the diffraction pattern be on a line perpendicular to the screen?[​IMG]

    I really do not where to start. Please help me out, i am so lost.
     
  2. jcsd
  3. Jun 9, 2006 #2

    Hootenanny

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    Well, do you know the condition / formula for single slit interfence?
     
  4. Jun 9, 2006 #3
    it's the one with the sin theta right or something right? please point me to the right track
     
  5. Jun 9, 2006 #4

    Hootenanny

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    I think this can be solved using the Fraunhofer Single Slit Diffraction relationship;

    [tex]a\sin\theta = m\lambda[/tex]

    Where a is the size of the slit, [itex]\lambda[/itex] is the wavelength and m is the order of the minima.
     
  6. Jun 9, 2006 #5
    ok ok i think i am remembering this now, and m would be 1 right for first null. when they say null they mean the minima fully destructive right
     
  7. Jun 9, 2006 #6

    Hootenanny

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    I am assuming that's what null means a minima (I haven't heard that terminology for a while). Yes, the fist minima would be at m = 1. This is different to maximas where the first maxima is at n = 1.
     
  8. Jun 9, 2006 #7
    ok thank you so much now i can find the angle easily
     
  9. Jun 9, 2006 #8

    Hootenanny

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