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Question: Answered & Verified by Expert
If the critical angle for total internal reflection from a medium to vacuum is $30^{\circ}$, the velocity of light in the medium is
PhysicsRay OpticsJEE Main
Options:
  • A $3 \times 10^8 \mathrm{~m} / \mathrm{s}$
  • B $1.5 \times 10^8 \mathrm{~m} / \mathrm{s}$
  • C $6 \times 10^8 \mathrm{~m} / \mathrm{s}$
  • D $\sqrt{3} \times 10^8 \mathrm{~m} / \mathrm{s}$
Solution:
2541 Upvotes Verified Answer
The correct answer is: $1.5 \times 10^8 \mathrm{~m} / \mathrm{s}$
$\begin{gathered}\mu=\frac{1}{\sin C}=\frac{1}{\sin 30}=2 \\ \therefore v=\frac{3 \times 10^8}{2}=1.5 \times 10^8 \mathrm{~m} / \mathrm{s}\end{gathered}$

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