Question

Light travel in two media A and B with speeds $1.8\times {10}^{8}m{s}^{-1}and2.4\times {10}^{8}m{s}^{-1}$ respectively. Then the critical angle between them is :

• A. $si{n}^{-1}\left(\frac{2}{3}\right)$
• B. $ta{n}^{-1}\left(\frac{3}{4}\right)$
• C. $ta{n}^{-1}\left(\frac{2}{3}\right)$
• D. $si{n}^{-1}\left(\frac{3}{4}\right)$

Answer 1

The correct option is D $si{n}^{-1}\left(\frac{3}{4}\right)$

Refractive index, $\mu =c/v$

${\mu }_1$=$\frac{3\times {10}^8}{1.8\times {10}^8}$

=$\frac{5}{3}$

${\mu }_2$=$\frac{3\times {10}^8}{2.4\times {10}^8}$

=$\frac{5}{4}$

Critical angle =$si{n}^{-1}\frac{1}{\mu }$

=$si{n}^{-1}\frac{3}{4}$