Q.How does the fringe pattern produced by interference at Young's double slit differ from the diffraction pattern produced at a single slit, in terms of

At a screen point $y$ from the centre in a $D\gg d$ double-slit set-up, the path difference is $\Delta\approx yd/D$ and the phase difference is $\phi=(2\pi/\lambda)\Delta$. A bright fringe (constructive interference, intensity $4I_0$) occurs when $\Delta …