JEE Main & Advanced
Physics
Question Bank
Prism Theory and Dispersion of Light
question_answer
Angle of a prism is 30° and its refractive index is \[\sqrt{2}\] and one of the surface is silvered. At what angle of incidence, a ray should be incident on one surface so that after reflection from the silvered surface, it retraces its path [MP PMT 1991; UPSEAT 2001; CBSE PMT 2004]
A) 30°
B) 60°
C) 45°
D) \[{{\sin }^{-1}}\sqrt{1.5}\]
Correct Answer:
C
Solution :
\[A=r+0\]\[\Rightarrow r={{30}^{o}}\] From Snell?s law at surface AB \[\mu =\frac{\sin i}{\sin r}\] \[\Rightarrow \sqrt{2}=\frac{\sin i}{\sin {{30}^{o}}}\Rightarrow i={{45}^{o}}\]