The refractive index of the materiel of a prism is 2 and the angle of the prism is 30 o . One of the two…

by principle of reversibility, the beam will return its path when it strikes the mirror perpendicularly

$r_2=0, r_1=A={30}^o$
$\therefore r_1+r_2=A$ in a prism
Applying Snell's law at P $\sin i=\sqrt{2}\sin {30}^o=\sqrt{2}\times \frac{1}{2}=\frac{1}{\sqrt{2}}$
$\angle i={45}^o$