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 intensity on the screen
`d sin theta = n lambda`
or `sin theta = (n lambda)/(d)`
`= ((n)(2000))/((7000)) = (n)/(35)`
`sin theta ge 12 implies n = 0, 1, 2, 3` only
Thus, only seven maxima can be obtained on both sides of the screen.