Young's double slit experiment is made in a liquid. The tenth bright fringe in liquid lies in screen where 6th dark fringe lies in vacuum. The refractive index of the liquid is approximately

Options

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

Answer

D

Explanation

Fringe width, `beta=(lambdaD)/(d)`
When the apparatus is immersed in liquid, wavelength becomes `(1)/(mu)` time and so does the fringe width.
As `10^(th)` bright fringe lies in liquid where `6^(th)` dark fringe lies in air. Therefore,
`x=10lambda.(D)/(d)=(2xx6-1)(lambda)/(2)(D)/(d)=5.5(lambdaD)/(d)`
or `(lambda)/(lambda)=(10)/(5.5)=1.8 "or" mu=1.8`