Q. A glass prism of refractive index 1.5 is immersed in water$\left( \mu = \frac{4}{3} \right).$Refer figure. A light beam incident normally on the face $AB$is totally reflected to reach the face $BC$if
A) $2/3 < \sin\theta < 8/9$
B) $\sin\theta\ \leq 2/3$
C) $\cos\theta\ \geq 8/9$
D) $\sin\theta > 8/9$
Explanation
(d) $\mu = \frac{9}{8}$
$\sin{C = \frac{1}{᷿\ _{w}\mu_{g}} = \frac{8}{9}}$
$C = \sin^{- 1}\left( \frac{8}{9} \right)$
$\theta > \sin^{- 1}\frac{8}{9}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.