How would the fringes on a given double slit apparatus change if you were to increase the width of each slit, without changing the centre-to-centre separation? Thanks

  • 2
    $\begingroup$ One can chug through the math to get there readily. $\endgroup$
    – Jon Custer
    Commented Nov 14, 2016 at 4:02
  • $\begingroup$ @JonCuster that isn't the slightest bit helpful. $\endgroup$
    – user135014
    Commented Nov 14, 2016 at 20:58
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    $\begingroup$ Jon Custer has a point. The diffraction of the double slit with finite slit width is standard fare in undergrad physics and the formula can be found in many textbooks and online. Did you look? $\endgroup$ Commented Oct 31, 2022 at 11:55

1 Answer 1


If both the slits were increased in width by equal amount, the pattern would look very similar except that the overall brightness of bright fringes increases since more light is able to enter, thus net intensity of light entering would increase.

Now if the increase in width is unequal then the minimum intensity of destructive interference would be non zero, hence the dark fringe would not look completely dark, but will have slight brightness.

But in both cases the pattern would not shift in any way.(Correct me if i am wrong).


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