Q. Light travels with a speed of $2\ \times 10^{8}{ms}^{- 1}$ in crown glass of refractive index 1.5. Whatis the speed of light in dense flint glass of refractive index 1.8?
A) $1.33\ \times \ 10^{8}{ms}^{- 1}$
B) $1.67\ \times \ 10⁸\ {ms}^{- 1}$
C) $2.0\ \times \ 10^{8}{ms}^{- 1}$
D) $3.0\ \times \ 10⁸\ {ms}^{- 1}$
Explanation
(b) $\mu = \frac{c}{v}$
$\therefore\frac{\mu}{\mu'} = \frac{v'}{v}$
$\frac{1.5}{1.8} = \frac{v'}{2 \times 10^{8}}$
$v^{'} = \frac{3 \times 10^{8}}{1.8} = 1.67 \times 10^{8}{ms}^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.