Question

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

• A. 1.8
• B. 1.54
• C. 1.67
• D. 1.2

Answer 1

The correct option is A 1.8

$y_{\text{bright}}=\frac{n\lambda D}{{\mu }_{liq}d}$

$y_{\text{dark}}=\frac{(2n-1)\lambda D}{2{\mu }_{vac}d}$

Given ${10}^{th}Bright=6^{th}$ dark in value

$\frac{10\lambda D}{{\mu }_{\text{liq}}d}=\frac{(2\times 6-1)\lambda D}{2\left(1\right)d}$

${\mu }_{liq}=1.81$