Q. When a ray of light is incident normally on one refracting surface of an equilateral prism (Refractive index of the material of the prism $= 1.5$)
A) Emerging ray is deviated by $30{^\circ}$
B) Emerging ray is deviated by $45{^\circ}$
C) Emerging ray just grazes the second refracting surface
D) The ray undergoes total internal reflection at the second refracting surface
Explanation
(d) Critical angle for the material of prism $C = \sin^{- 1}\left( \frac{1}{\mu} \right) = \sin^{- 1}{\left( \frac{1}{1.5} \right) = 42{^\circ}}$ since angle of incidence at surface $AB(60{^\circ})$ is greater than the critical angle $(42{^\circ})$, so total internal reflection takes place
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.