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 $\left. c =3 \times 10^{8}\, ms ^{-1}\right)$

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

Answer 1

Answer: (C)

$v =\frac{ c }{\mu}$
$\Rightarrow v _{ B }=\frac{3 \times 10^{8}}{1.47}=2.04 \times 10^{8}=20.4 \times 10^{7} m / s$
$\because v _{ A }- v _{ B }=2.6 \times 10^{7} m / s$
$\therefore v _{ A }-(20.4+2.6) \times 10^{7}-23 \times 10^{7} m / s$
$\therefore \frac{\mu_{ B }}{\mu_{ A }}=\frac{ v _{ A }}{ v _{ B }}=\frac{23 \times 10^{7}}{20.4 \times 10^{7}}=1.13$