Wave Theory, Wavefronts & Doppler Effect question from NEET 2023

Answer: (a)

1. Green just grazes the surface, so the angle of incidence equals the critical angle for green.
2. $\sin C = 1/\mu$; colours with smaller $\mu$ (longer $\lambda$) have a larger critical angle, so for them $i < C$ and they refract out.
3. Blue and violet have larger $\mu$, so $i > C$ and they are totally internally reflected.
4. So the answer is (a) yellow, orange and red.