In diffraction experiments interference takes place along with diffraction? Does diffraction take place in Young's double slit experiment? If it does take place then why don't we get the pattern of diffraction experiment on the screen?


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Both diffraction and interference occur in the double slit experiment. The wavefront is diffracted as it passes through each of the slits. The diffraction causes the wavefronts to spread out as if they were coming from light sources located at the slits. These two wavefronts overlap, and interference occurs. This is what give the diffraction pattern.

I think what you are confused about is the single slit experiment. In the single slit experiment, light passes through a single slit which produces an interference pattern. This not do to diffraction of the light. In the single slit experiment, the slit is large enough that diffraction does not occur. Instead every point along the width of the slit acts like it's own point light source, which all interfere with one another. In fact, if you make the slit narrow enough in the single slit experiment, diffraction occurs and the interference pattern goes away.

  • $\begingroup$ Maybe my explanation wasn't that clear. This thread explains single slit interference in detail physics.stackexchange.com/questions/61455/… $\endgroup$
    – user235504
    Nov 20, 2015 at 11:37
  • $\begingroup$ Even behind a single slit the overall dimension of the intensity distribution is broader as the slit. Hence diffraction takes place. Amazingly the same happens behind any sharp edge to. $\endgroup$ Nov 20, 2015 at 11:41
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    $\begingroup$ @Robert_Stiffler this is a totally WRONG answer: both diffraction and interference occur simultaneously in any scattering, they never ever exist by themselves. Your implicit reference to Huygens' principle does in fact contain the answer: the interfering spherical wavelets while are interfering they do also diffract around the edges, that is how you get a smooth spherical wave surface in the middle and little sidelobes on the side of the slit. $\endgroup$
    – hyportnex
    Nov 20, 2015 at 12:56

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