question_answer

One face AC of the glass prism is silvered as shown and the principal section of a glass prism is an isosceles triangle ABC with AB = AC. The \[\angle BAC\], if the ray incident normally on the face AB and after two reflections, it energies from the base BC perpendicular to it, is

A) 70°                                            

B) 36°

C) 72°                                            

D) 44°

Correct Answer: B

Solution :

\[\alpha +2\beta ={{180}^{\circ }}\] and \[\beta =2\alpha \] \[\therefore \]  \[\alpha ={{36}^{\circ }}\]