A monochromatic light wave is incident normally on a glass slab of thickness d , as shown in the figure. The…

A monochromatic light wave is incident normally on a glass slab of thickness d, as shown in the figure. The refractive index of the slab increases linearly from n1 to n2 over the height h. Which of the following statement(s) is(are) true about the light wave emerging out of the slab?

  1. It will deflect up by an angle tan-1n22-n12d2h
  2. It will deflect up by an angle tan-1n2-n1dh
  3. It will not deflect
  4. The deflection angle depends only on (n2-n1) and not on the individual values of n1 and n2

Solution

\(t=\frac{d}{\frac{c}{n_1}}=\frac{n_1 d}{c}\) in time t wavefront at B travel \(\mathrm{S}_1 ; S_1=\frac{c}{n_2} \times \frac{n_1 d}{c} \Rightarrow \frac{d n_1}{n_2}\) When the wave front of \(\mathrm{B}\) reaches at the end of the slab then \(\mathrm{t}_1=\left(\frac{d-s_1}{c}\right) n_2 \Rightarrow \frac{d\left[n_2-n_1\right]}{c}\) in \(\mathrm{t}_1\) time, wavefront at \(\mathrm{A}\) travel \(\Rightarrow \mathrm{S}_2\) \(\begin{aligned} & \mathrm{S}_2=\mathrm{ct}_1=\mathrm{d}\left[\mathrm{n}_2-\mathrm{n}_1\right] \\ & \tan \theta=\frac{\left(n_2-n_1\right) d}{n} \Rightarrow \theta=\tan ^{-1} \frac{\left(n_2-n_1\right) d}{h} \end{aligned}\)

Asked in: JEE Advanced 2023 (Paper 2)

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