But, \(\Delta \phi=\frac{2 \pi}{\lambda} \Delta x\)
so, \(\Delta x=\frac{\lambda}{4}\)
\(\frac{d y}{D}=\frac{\lambda}{4}\) ..... \((i)\)
\({\frac{{\lambda D}}{d} = \beta }\) ..... \((ii)\)
Multiplying equation \((i)\) and \((ii)\) we get,
\(y=\frac{\beta}{4}\)