In Young's double slit experiment how many maxima 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. 12
B. 7
C. 18
D. 4

Answer

B

Explanation

For maximum (brightness) intensity of the screen path difference should be integer multiple of wavelength i.e.,
`d sin theta=nlambda`
`sin theta=(nlambda)/d=(n(2000))/7000=n/(3.5)`
As, `(sin theta)_(max)=1`
So, `n=0,1,2,3`
Thus, only seven maximas can be obtained on both sides of the screen.