A ray of light incident normally on a prism of 60 degree angles .Show the path of the light ray till it emerges out of the prism. The critical angle of glass is 42 degree

Light ray incident normally on side of prism at A . As seen from figure , light ray incident with angle of incidence 60^o at B on oposite side .

 

Since angle of incidence is greater than critical angle , total internal reflection is taking place at B. 

Hence light ray is reflected at B with angle of reflection 60^o .

 

As can be seen from figure , reflected light ray makes normal incidence  at C on third side of prism .

Hence the light ray emerges out of the prism by making angle 90^o with the third side of prism.

 

Conclusion :-

If light ray makes normal incidence at one side , then it emerges out from third side by making 90^o with third side .

 

Overall deviation is 60^o