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Diffraction by single slit - effect of increasing the slit width

  1. Aug 1, 2005 #1
    For diffraction by a single slit, what is the effect of increasing (a) the slit width, and (b) the wavelength? It was a problem on my daughter's final and I never seemed to be able to answer it for her. :confused:
  2. jcsd
  3. Aug 1, 2005 #2


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    The answer lies in the fact that the minima are located at intervals of [itex]n\lambda / D[/itex] (value of sin)... so a bigger slit (D) makes narower maxima and a larger wavelenght ([itex]\lambda[/itex]) makes wider maxima.
  4. Aug 1, 2005 #3
    for single-slit diffraction, the condition for MINIMUMs is:

    [tex] y \ = \ \frac{m \lambda D}{s} [/tex]

    where y is the distance from central max to the m-th minimum of the diffraction pattern, m a positive integer, λ the wavelength, D the distance between single-slit and distant observation screen where diffraction pattern will be observed, and s the single-slit width. Thus:
    a) increasing single-slit width will decrease width of central max ("shrink the diffraction pattern");
    b) increasing wavelength will increase width of central max ("expand the diffraction pattern")
    Last edited: Aug 1, 2005
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