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. (a) `1.59`
B. (b) `1.69`
C. (c) `1.78`
D. (d) `1.25`

Answer

C

Explanation

`(y_8)_(Bright, medium)=(y_5)_(Dark, air)`
`(8lambda_mD)/(d)=((2(5)-1)/(2))(lambdaD)/(d)`
`(8lambda)/(mu)D/d=9/2(lambdaD)/(d)impliesmu=16/9=1.78`