Total Internal Reflection question from NEET 2010 (AIPMT, Mains)

Answer: (c)

1. $\sin C = \frac{v_1}{v_2} = \frac{1.5}{2.0} = \frac{3}{4}$, so $C = \sin^{-1}\left(\frac{3}{4}\right)$.
2. TIR (total reflection) needs $i \geq C$ (at $i = C$ the ray just grazes).
3. So the answer is (c) $i \geq \sin^{-1}\left(\frac{3}{4}\right)$.