Question

A ray of light enters into benzene from air. If the refractive index of benzene is $1.50$, by what percent does the speed of light reduce on entering the benzene?

Answer 1

$\eta =\frac{c}{v}$

where, $c=$speed of light in vaccum

Given,

${\eta }_{benzene}=1.50$

we know, $c=3\times {10}^{8}m/s$ & $\eta =\frac{c}{v}$

$\therefore v_{benzene}=\frac{c}{\eta }=\frac{3\times {10}^8}{1.5}=2\times {10}^8$ m/s

$\%$ Reduction in speed of light

$=\frac{c-v}{c}\times 100$

$=\frac{3\times {10}^8-2\times {10}^8}{3\times {10}^8}\times 100$

$=\frac{{10}^8}{3\times {10}^8}\times 100$

$=33.33\%$.