Q 12-08-146JEE MainJEE Main 2022 (28 Jul, Shift 1)Easy
Light travelling in air passes through medium 1 ($\mu_r = 1$, $\varepsilon_r = 4$) and then into medium 2 ($\mu_r = 1$, $\varepsilon_r = 9$). The speed of light $v_2$ in medium 2 will be :
(Given $c = 3\times10^8\ \text{m s}^{-1}$)
Answer: (A) $1.0\times10^8\ \text{m s}^{-1}$
The speed in a medium depends only on that medium:
$$v_2 = \frac{c}{\sqrt{\mu_r\varepsilon_r}} = \frac{3\times10^8}{\sqrt{1\times9}} = 1.0\times10^8\ \text{m s}^{-1}$$
Solution by Sreeraj P, M.Sc Physics