question_answer

The refractive index of the material of a prism is \[\sqrt{2}\] and its refracting angle is \[30{}^\circ \]. One of the refracting surfaces of the prism is made a mirror inwards. A beam of monochromatic light entering the prism from the other face will retrace its path after reflection from the mirrored surface if its angle of incidence on the prism is: [AIPMT (S) 2004]

A)        \[45{}^\circ \]          

B)   \[60{}^\circ \]

C)  \[0{}^\circ \]        

D)   \[30{}^\circ \]

Correct Answer: A

Solution :

According to the given condition, the beam of light will retrace its path after reflection from BC.  So

Thus, angle of refraction at surface AC

By Snell's law