Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is $\frac{3

Question

Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is $\frac{3}{2}$ is\

Professor PC Thomas Classes · Answer

(c) : $v_{g}=\frac{c}{\mu}=\frac{3 	imes 10^{8}}{3}=2 	imes 10^{8} \mathrm{~m} / \mathrm{s}$ $$ t=\frac{x}{v_{g}}=\frac{4 	imes 10^{-3}}{2 	imes 10^{8}}=2 	imes 10^{-11} \mathrm{~s} $$