Question

The time taken by light to pass through $4\, mm$ thick glass slab of refractive index $1.5$ will be : (velocity of light in air $\left.=3 \times 10^{8} m / s \right)$

• A. $ 8\times 10^{-11}s $
• B. $ 2\times 10^{-11}s $
• C. $ 8\times {{10}^{-8}}s $
• D. $ 2\times 10^{-8}s $

Answer 1

Answer: (B)

Time taken by light
$t =\frac{\mu d}{c}$
$=\frac{1.5 \times 4 \times 10^{-3}}{3 \times 10^{8}}=2 \times 10^{-11} s$