Show that no ray can pass through a prism whose refracting angle A is greater than twice the critical angle for the material of  the prism.

From the above diagram its clear that no ray can pass through a prism whose refracting angle A is greater than twice the critical angle for the material of  the prism because even for the limiting case of grazing incidence the light is not able to pass as the incidence angle at second surface becomes more equal to critical angle, so for other cases it is immpossible for it to pass throgh prism.