In Young's double slit experiment how many maximas can be obtained on a screen (including the central maximum) on both sides of the central fringe if λ = 2000Å and d = 7000Å

7

For maximum intensity on the screen

$d \sin \theta=n \lambda \Rightarrow \sin \theta=\frac{n \lambda}{d}=\frac{n(2000)}{7000}=\frac{n}{3.5}$

Since maximum value of sin θ is 1

So n = 0, 1, 2, 3, only. Thus only seven maximas can be obtained on both sides of the screen.