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 `lambda=2000Å` and `d=7000Å`

Options

A. (a) `12`
B. (b) `7`
C. (c) `18`
D. (d) `4`

Answer

B

Explanation

For maximum intensity on the screen
`d sin theta=nlambdaimpliessin theta=(nlambda)/(d)=(n(2000))/(7000)=(n)/(3.5)`
Since maximum value of `sin theta` is `1`.
So `n=0, 1, 2, 3` only. Thus only seven maximas can be obtained on both sides of the screen.