Question

A ray of monochromatic light is incident on one refracting face of a prism of angle $ 75{}^\circ $ . It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the material of prism is $ \sqrt{2,} $ , the angle of incidence on the first face of the prism is :

• A. $ 0{}^\circ $
• B. $ 60{}^\circ $
• C. $ 45{}^\circ $
• D. $ 30{}^\circ $

Answer 1

Answer: (C)

For critical angle $ Sin\,\,C=\frac{1}{\mu } $ $ \sin \,C=\frac{1}{\sqrt{2}}=\sin {{45}^{o}} $ $ C={{45}^{o}} $ it means angle of emergence $ e={{45}^{o}} $ For prism angle of incident I = $ e={{45}^{o}} $