Young's double slit experiment is made in a liquid. The 10th bright fringe in liquid lies where 6th dark fringe lies in air. The refractive index of liquid is .......

Options

A. `1.2`
B. `1.6`
C. `1.5`
D. `1.8`

Answer

D

Explanation

Since apparatus of experiment is immerged in liquid hence wavelength will be `(1)/(mu)` th times and width of fringe also become `(1)/(mu)` th times.
The `10^(th)` bright fringe is found in the liquid,
`:.x=(10 lambda.D)/(d)" "......(1)`
The `6^(th)` bright fringe is found in the liquied
`:. x=(2xx6-1)(lambda)/(2D)=(11lambdaD)/(2d) " "....(2)`
Equation (1) and (2) are equal
`:.(10 lambda.D)/(d)=(11lambda D)/(2d)`
`(20)/(11)=(lambda)/(lambda)`
`:. n=1.818`