Q 12-08-148JEE MainJEE Main 2021 (27 Jul, Shift 1)Easy
The relative permittivity of distilled water is $81$. The velocity of light in it will be: (Given $\mu_r = 1$)
Answer: (C) $3.33\times10^7\ \text{m s}^{-1}$
$$v = \frac{c}{\sqrt{\mu_r\varepsilon_r}} = \frac{3\times10^8}{\sqrt{81}} = \frac{3\times10^8}{9} = 3.33\times10^7\ \text{m s}^{-1}$$
Solution by Sreeraj P, M.Sc Physics