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Homework Help: Diffraction problem II

  1. Mar 14, 2007 #1
    1. The problem statement, all variables and given/known data

    Hello,I have done this problem.Please check if it is correct.

    Fraunhofar double slit diffraction pattern is observed on the focal plane of a lens of focal length 0.5m;wavelength of incident light used is 500nm;The distance between the maxima adjacent to the zeroth order maxima is 5mm & the 4th order is missing.Find the distance between their centres

    2. Relevant equations

    3. The attempt at a solution

    linear distance between maximas y = f sin θ
    if θ is small sin θ = θ so θ = y/f = 5mm/0.5m
    maximas are obtained (e+d) sin θ = n λ
    n = 1 for maxima and zeroth maxima (e+d) θ = λ
    (e+d) = λ / θ
    e-slit width d-distance between the centres
    (e+d) = 5*10^-5
    condition of missing (e+d)/e = 4 { 4- order missing}
    4e = 5*10^-5 so e = 1.25*10^-5
    from the condition of missing e+d =4e so d = 3e
    distance between the centres d = 3* 1.25*10^-5
  2. jcsd
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