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Earlier discussion
3 older comments kept for context.
Victor Titus
The ray enters the prism without deviation since it strikes side AB normally. It then makes an incidence angle of 45.0° with normal to side AC. The critical angle of the prism must be smaller than 45.0° if the ray is to be totally reflected at side AC and thus turned through 90°.
Osuji Chiamaka
This is not correct
Sin I/sin r=sin 90°/sin40°=1/0.7071=1.41
Oluwaseun Adeyemi
Refractive index of a glass prism, M = 1.50