AIPMT 2004 Physics and Chemistry Paper

The refractive index of the material of a prism is √2 and its refracting angle is 30∘. 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 form the mirrored surface if its angle of incidence on the prism is :-