Question

A glass prism of refractive index 1.5 is immersed in water (refractive index $\frac{4}{3}$). A light beam normally on the face AB is totally reflected to reach on the face BC if

• A. $sin\theta \ge \frac{8}{9}$
• B. $\frac{3}{2}<sin\theta \ge <\frac{8}{9}$
• C. $sin\theta \le \frac{3}{2}$
• D. $sin\theta \le \frac{8}{9}$

Answer 1

The correct option is A $sin\theta \ge \frac{8}{9}$

for TIR , incidence angle should be more than critical angle. Find the critical angle using snells law and get the answer to be $sin\theta \ge \frac{8}{9}$