In deriving the single slit diffraction pattern, it was stated that the intensity is zero at angle `n lambda//a`. Justify this by suitable dividing the slit to bring out the cancellation.

Explanation

Divide the single slit into n smaller slits of width `a ′ = a//n.` The angle `theta=nlambda//a=lambda//a.`. Each of the smaller slits sends zero intensity in the direction θ. The combination gives zero intensity as well.