A parallel beam of light falls normally on the first face of a prism of small refracting angle. At the second refracting face it is partly reflected and partly transmitted. The reflected light strikes the first face again and emerges from it making an angle of `4°` with the reversed direction of incident beam. The deviation suffered by refracted ray is `1°` from original direction of incident ray. Find the refractive index of glass of the prism and the angle of the prism.
