Young's double slit experiment is first performed in air and then in a medium other than air. It is found that `8^(th)` bright fringe in the medium lies where `5^(th)` dark fringe lies in air. The refractive index of the medium is nearly:

Options

A. `1.59`
B. `1.69`
C. `1.78`
D. `1.25`

Answer

C

Explanation

`(8D(lambda//mu))/d=((2xx4+1)Dlambda)/(2d)`
`mu=16/9=1.78`