I am looking for the distance between the 2nd and 3rd DARK fringes on a screen.(adsbygoogle = window.adsbygoogle || []).push({});

Monochromatic, coherent light is shone through 2 slits a distance d apart.

Wavelength is L. Distance between grating and screen is R.

The formula I am using is: [(R(5/2)L)/d - (R(3/2)L)/d]

I am using 5/2 and 3/2 since these should be the number of wavelengths for destructive interference for the 3rd and 2nd fringes respectively.

The formula doesn't seem to be working though. Where have I gone wrong????

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# Homework Help: Destructive interference and fringes

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