Question

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 $30V/m$, then the amplitude of the electric field (in V/m) for the wave propogating in the glass medium will be:

Answer 1

Answer: 24

As $4\%$ of light gets reflected, so only $(100-4=96\%)$ of light comes after refraction so,
$P_{\text{refracted}}=\frac{96}{100}{P}_1$
$\Rightarrow K_2{A}_t^2=\frac{96}{100}{K}_1{A}_i^2$
$\Rightarrow r_2{A}_t^2=\frac{96}{100}{r}_1{A}_i^2$
$\Rightarrow A_t^2=\frac{96}{100}\times \frac{1}{\frac{3}{2}}\times (30{)}^2$
$A_t\sqrt{\frac{64}{100}\times (30{)}^2}=24$