Light travels from water (refractive index $n_1=1.33$) to air ($n_2=1.0$). The ray makes an angle of 50° with the normal while in water. Determine whether the light will refract into the air or undergo total internal reflection.

Step-by-step solution

1. Calculate the critical angle: $\sin {\theta }_c=n_2/n_1=1/1.33=0.7519$.
2. Find ${\theta }_c=\arcsin (0.7519)\approx 48.75°$.
3. Compare with the given incidence of 50°: $50°>48.75°$, so the ray exceeds the critical angle.
4. Therefore the light undergoes total internal reflection and does not refract into air.

Concept tested: Total internal reflection

Published 7 October 2026 · How this solution was prepared and checked