Question

The difference of speed of light in the two media $A$ and $B\left(v_A-v_B\right)$ is $2.6\times 10^{7}m/s$. If the refractive index of medium $B$ is $1.47$, then the ratio of refractive index of medium $B$ to medium $A$ is : (Given : speed of light in vacuum $c=3\times 10^{8}m{s}^{-1})$

• A. 1.303
• B. 1.318
• C. 1.13
• D. 0.12

Answer 1

Answer: (C)

$v=\frac{c}{\mu }$
$\Rightarrow v_B=\frac{3\times 10^8}{1.47}=2.04\times 10^8=20.4\times 10^{7}m/s$
$\because v_A-v_B=2.6\times 10^{7}m/s$
$\therefore v_A-(20.4+2.6)\times 10^7-23\times 10^{7}m/s$
$\therefore \frac{{\mu }_B}{{\mu }_A}=\frac{v_A}{v_B}=\frac{23\times 10^7}{20.4\times 10^7}=1.13$