A symmetric triangular prism made of flint glass ( ) has an apex angle of
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A symmetric triangular prism made of flint glass (n=1.60) has an apex angle of 30∘. The prism is fully immersed in water (n=1.33). A narrow light beam in the water approaches one face of the prism in a plane perpendicular to the prism’s edge. The beam is incident at an angle of 10∘ above the normal to that face.
(1) Determine the angle that the beam makes with the normal inside the glass after crossing the first interface.
(2) Using geometric relations within the prism, calculate the angle at which the beam reaches the second face, measured inside the prism relative to the normal of that face.
(3) Evaluate whether total internal reflection occurs at the second face. Show all reasoning and state the relevant numerical condition clearly.
(4) If the beam refracts out of the prism, calculate the angle it makes with the normal in the surrounding water as it emerges. If instead total internal reflection occurs, determine the angle of reflection inside the prism and describe the subsequent path of the beam until it re-enters the water.