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Homework Help: Optics Question (I think about Fresnel-Kirchoff)

  1. Mar 6, 2009 #1
    1. The problem statement, all variables and given/known data
    A laser produces a beam of coherent light of wavelength lambda with plane
    wave-fronts travelling along z. The amplitude of light transmitted by a trans-
    parency in the x; y plane is independent of y and varies with x as

    A[1 + cos(2*pi*x/d)]

    where A is a constant and d > lambda. Show that three beams emerge
    from the transparency, and find their angles to the z-axis.

    2. Relevant equations

    I think:

    A(B) ~ int[u(x) exp(-iBx)]

    Where B=k*sin(theta), u is the amplitude distribution given and A(B) is the amplitude at some theta.

    3. The attempt at a solution
    So I tried using that equation, hoping that only 3 values of theta would be valid or something, but it just didn't work at all. Am I completely off?

  2. jcsd
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