The following diagram shows a `60^(@),30^(@),90^(@)` glass prism of critical angle `42^(@)`. Copy the diagram and complete the path of incident ray AB emerging out of the prism marking the angle of incidence on each surface.

Explanation

Since critical angle of prism
`i_c = 42^@ ,` for given ray AB incident on surface XZ at an angle of incidence of 30°, and refracted out from prism ` ( :. mu = (1)/( sin i_c))`
The angle of refraction is given by, `mu sin r =1.sinr = ( sin 30^@)/( sin 42^@) = ( 0.5 ) /( 0.669 ) = 0.75 = r= 40^@ `