Q 12-08-215JEE MainJEE Main 2019 (12 Jan, Shift 1)Medium
A light wave is incident normally on a glass slab of refractive index $1.5$. If $4\%$ of light gets reflected and the amplitude of the electric field of the incident light is $30$ V/m, then the amplitude of the electric field for the wave propagating in the glass medium will be:
Answer: (C) $24$ V/m
$96\%$ of the intensity enters the glass. Intensity in a medium is $\dfrac12\varepsilon_0cnE^2$, so
$$n E_t^2 = 0.96E_0^2 \Rightarrow 1.5E_t^2 = 0.96\times900 \Rightarrow E_t^2 = 576$$
$$E_t = 24\ \text{V/m}$$
Solution by Sreeraj P, M.Sc Physics