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Interference pattern problem

  1. Mar 4, 2006 #1
    Anyone can help me on this one.

    A plane wave of wavelength [tex]\lambda[/tex]= 550 nm is incident normally on an opaque screen with three narrow parallel slits separated by distance a= 2.3 mm. An interference pattern is observed on the other side of the screen at a large distance from it.
    (a)At what angles are the first principal maxima adjacent to the central maximum?
    (b)How does intensity, Imax, at the principal maxima compare to that from a single slit, I1?

    in (a) can I use asin[tex]\theta[/tex]=m[tex]\lambda[/tex] to get the angle?
  2. jcsd
  3. Mar 4, 2006 #2
    from my notes (as im studying this aswell) i believe your answer from (b) should lie.... or could possibly be I= N^2 * Io

    for a i would use asin[tex]\theta[/tex]=m[tex]\lambda[/tex] aswell but im not so sure on this one, optics isn't exactly my best subject at the moment
  4. Mar 5, 2006 #3
    For a maximum, the amplitudes will add in phase when a.sin(theta) = lambda, if a is the slit-to-slit spacing. For a minimum, you have to figure out when 3 waves will add to zero. The intensity is proportional to the square of the sum of the amplitudes.
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