Figure shows the section of a semi-circular glass slab having its centre at O. three rays of light A,B and C of the same colour are incident on the slab and strike on the edge XY at the point O. the light ray B suffers refraction along OB'. (a) On the diagram, mark the critical angle by C. (b) The rays enter the slab undeviated. give reason. (c) Draw the path of rays A and C after they strike the edge XY. (d) Name the phenomenon which the rays A and C exhibit.

Figure shows the section of a semi-circular glass slab having its cent

1.	Figure shows the section of a semi-circular glass slab having its centre at O. three rays of light A,B and C of the same colour are incident on the slab and strike on the edge XY at the point O. the light ray B suffers refraction along OB'. (a) On the diagram, mark the critical angle by C. (b) The rays enter the slab undeviated. give reason. (c) Draw the path of rays A and C after they strike the edge XY. (d) Name the phenomenon which the rays A and C exhibit.
Answer» Solution :(a) In FIGURE, the critical angle has been marked as C which is the angle of incidence for the ray B. (b) Each of the rays A, B and C is incident normally on the SLAB along its radius, so it enters the slab undeviated. (c) Figure shows the PATH of the rays A and C after they strik the edge XY and OA. and OC. RESPECTIVELY. (d) The ray A suffers refraction from glass to air while the ray C suffers TOTAL internal reflection.