Physics Help Forum 4 slit interference with unequal spacing

 Jan 14th 2015, 02:55 AM #1 Junior Member   Join Date: Jan 2015 Posts: 2 4 slit interference with unequal spacing Hi all I'm currently working on something and need a little help. I have very limited knowledge in this area, so please bare with me, but if anyone can provide some pointers then please do. Basically, I need to derive some kind of equation to simulate a 4 slit interference pattern, where the slits are spaced at unequal intervals (that I can set). I'm aware that this may result in one, or a series of, long and complicated formula, but I'll be running it through excel (or something), so that doesn't really matter. There are loads of derivations of equally spaced slits, but I don't really know how to manipulate this to cater for the unequal spacings. I have found a derivation using 'phasors' of two slit interference, giving; I = I_0 * (cos(del/2))^2 where del = (2 * pi/wavelength) * a * sin(theta) as is covered elsewhere on the net. This phasor derivation makes sense to me, but expanding it seems to over-simplify it; I don't think I'm doing it correctly. I guess I just need to add to this the effect of another slit, and then again, but I'm not sure how to go about it. Does anyone have any pointers? Thanks
 Jan 14th 2015, 07:54 AM #2 Senior Member     Join Date: Apr 2008 Location: Bedford, England Posts: 668 I would think that you should be able to treat each pair of slits independently, then superimpose (add) the results. Note that for 4 slits you have 6 different ways to combine these into pairs. __________________ You have GOT to Laugh !
Jan 14th 2015, 08:16 AM   #3
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Join Date: Jan 2015
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 Originally Posted by MBW I would think that you should be able to treat each pair of slits independently, then superimpose (add) the results. Note that for 4 slits you have 6 different ways to combine these into pairs.

I'm looking into this; I need to plot the intensity as a function of the angle from 'straight ahead' if that makes sense. That makes this slightly more problematic, although I guess I could make that conversion later on in the process.

 Tags interference, slit, spacing, unequal

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