Question

Light travels in two media $A$ and $B$ with speeds $1.8 \times 10^8 ms^{-1}$ and $2.4 \times 10^8 ms^{-1}$ respectively. Then the critical angle between them is

• A. $\sin^{-1} \bigg(\frac{2}{3}\bigg)$
• B. $\tan^{-1} \bigg(\frac{3}{4}\bigg)$
• C. $\tan^{-1} \bigg(\frac{2}{3}\bigg)$
• D. $\sin^{-1} \bigg(\frac{3}{4}\bigg)$

Answer 1

Answer: (D)

$\sin^{-1} \bigg(\frac{3}{4}\bigg)$

Answer 2

We have
$C= sin^{-1} \bigg(\frac{v_1}{v_2}\bigg)$
$= sin^{-1} \bigg(\frac{1.8 \times 10^8}{2.4 \times 10^8}\bigg)=sin^{-1} \bigg(\frac{3}{4}\bigg)$