Q. Refractive index of glass with respect to medium is$\frac{4}{3}$. If the differences between velocities of light in medium and glass is $6.25\ \times \ 10^{7}{ms}^{- 1},$ then velocity of light in medium is
A) $2.5\ \times \ 10^{8}{ms}^{- 1}$
B) $0.125\ \times \ 10^{8}{ms}^{- 1}$
C) $1.5\ \times \ 10^{8}{ms}^{- 1}$
D) $3\ \times \ 10^{8}{ms}^{- 1}$
Explanation
(a) So, velocity of light in glass
$V_{g} = \frac{V_{m}}{\mu}$
$V_{m} - V_{g} = V_{m} - \frac{V_{m}}{\mu}$
$\therefore\ 6.25 \times 10^{7} = V_{m}\left( 1 - \frac{1}{\frac{4}{3}} \right)$
$V_{m} = 6.25\ \times 10^{7} \times 4$
$= 2.5\ \times 10^{8}ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.