Question

A glass prism of refractive index $1.5$ is immersed in water (refractive index $4/3$). A light beam incident normally on the face:$AB$ as shown in the figure is totally reflected to reach the face $BC$ if:

• A. $\sin \theta >8/9$
• B. $2/3<\sin \theta <8/9$
• C. $\sin \theta \le 2/3$
• D. $noneoftheabove$

Answer 1

The correct option is A $\sin \theta >8/9$

$\begin{array}{c}\text{Condition for}Refraction{\mu }_1\sin {\theta }_1,>{\mu }_2\sin {\theta }_2\\ 1.5\sin \theta \cdot >\frac{4}{3}\sin \left(90\right)\\ \sin \theta >\frac{8}{9}\\ \text{So option}A\text{is correct}\end{array}$