The time taken by light to travel normally through a glass plate of thickness 1 mm would be: (Take refractive index of glass = 1.5)
Answer & explanation
Correct answer: option 3
$ V = \frac{c}{\mu} = \frac{3\times 10^8}{1.5} = 2\times 10^8$
$ t = \frac{d}{v} = \frac{10^{-3}}{2\times 10^8} = 5\times 10^{-12} s$