b
(b)For maxima \(\Delta = d\sin \theta = n\lambda \)
==> \(2\lambda \sin \theta = n\lambda \)==> \(\sin \theta = \frac{n}{2}\)
since value of sin \(\theta\) can not be greater \(1.\)
\( n = 0, 1, 2\)
Therefore only five maximas can be obtained on both side of the screen.