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# A ray of light passes through four transparent media with refractive indices $\mu_1, \mu_2, \mu_3$ and $\mu_4$ as shown. The surface of all media are parallel. The emerging say CD is parallel to incident ray AB, Then ,

$\begin{array}{1 1} (a)\;\mu_1=\mu_2 \\ (b)\;\mu_2=\mu_3 \\ (c)\;2 \mu_1 =\mu_3 \\ (d)\;\mu_4=\mu_1 \end{array}$

W know for any two medium
$\mu_1 \sin i_1 =\mu_2 \sin i_2$
(ie) $\mu \sin i = constant$
Since $AB$ is parallel to $CD$
$i _B=i_C$
$\mu_1 \sin i_B =\mu _4 \sin i_c$
$\mu_1 =\mu_4$
Hence D is the correct answer.