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If smoke is present in between the screen and slit in Young's double slit experiment using laser, will there be any change in the interference pattern? Will the fringes be obtained on the screen?

Smoke has large particles in it and I think they can diffract light because smoke particles have sizes comparable to wavelength of light. Also, the smoke will have a different refractive index and hence can change the optical path of light which will affect the fringe pattern.

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Yes it would depending on how thick the smoke was. Photons intercepted by the smoke would be scattered or absorbed but the photons that still have a clear shot to the screen would contribute to the original fringe pattern. The pattern would still be the same but not as clear.

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    $\begingroup$ I just set up an experiment with laser and slit at about three meters from the screen. I measured the fringes before and after introducing smoke and it made no change that I could tell. $\endgroup$ – Bill Alsept Feb 4 '16 at 2:14
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    $\begingroup$ You expect a reduction in contrast, depending on the concentration of smoke. Because you are looking "through a fog". $\endgroup$ – Floris Feb 4 '16 at 3:41
  • $\begingroup$ Yes it was not clear just like we thought, but more to what I think the OP was asking the smoke did not effect the pattern of the fringes. They stayed the same. $\endgroup$ – Bill Alsept Feb 4 '16 at 3:46
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    $\begingroup$ The light you saw on the smoke was scattered, not absorbed... $\endgroup$ – Floris Feb 4 '16 at 11:29
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    $\begingroup$ You think so? I was thinking it was absorbed and then re emitted like when light reflects off of a wall or clouds reflecting light back out into space. I always though scatter meant a little to the left or right but not straight back. $\endgroup$ – Bill Alsept Feb 4 '16 at 15:25
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I have introduced a Halloween fogger during a double slit experiment and have introduced cigar smoke as well. The only affect was dimming. The patterns were unchanged. It does allow you the view the light traveling to the screen though. Give it a try; it’s pretty easy to setup. Maybe you’ll see something that everyone else has missed.

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The smoke will blur the pattern, so yes it does affect it. The blur can be seen as loss of coherence and coherence is needed for the interference.

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