1. Tardigrade
  2. Question
  3. Physics
  4. 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 (in V/m) for the wave propogating in the glass medium will be:

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Q. 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 (in V/m) for the wave propogating in the glass medium will be:

Ray Optics and Optical Instruments

Solution:

As $4\%$ of light gets reflected, so only $(100 - 4 = 96\%)$ of light comes after refraction so,
$P_{\text{refracted}} = \frac{96}{100} P_1$
$\Rightarrow K_2 A^2_t = \frac{96}{100} K_1A^2_i$
$\Rightarrow r_2 A^2_t = \frac{96}{100} r_1 A^2_i$
$\Rightarrow A^2_t = \frac{96}{100} \times \frac{1}{\frac{3}{2}} \times (30)^2$
$A_t \sqrt{\frac{64}{100} \times (30)^2} = 24$