Correct Answer - D
The path difference introduced due to introduction of transparent sheet is given by `Deltax=(m-1)t`.
If the central maxima occupies position of nth fringe, then
`(mu-1)t=nlambda=dsintheta`
`sin theta=((mu-1)t)/(d)=((1.17-1)xx1.5xx10^-7)/(3xx10^-7)=0.085`
Hence the angular position of central maxima is
`theta=sin^-1(0.085)=4.88^@`
For small angles `sin theta~=theta~=tantheta`
`tantheta=y/D`
`y/D=((mu-1)t)/(d)`
Shift of central maxima is `y=(D(mu-1)t)/(d)`
This formula can be used if D is given.