. R EFRACTION THROUGH A P RISM Figure . shows the passage of light through a triangular prism ABC. The angles of incidence and refraction at the first face AB are i and r , while the angle of incidence (from glass to air) at the second face AC is r !
and the angle of refraction or emergence e. The angle between the emergent ray RS and the direction of the incident ray PQ is called the angle of deviation , .