Question

Light passes through a rectangular glass slab and through a triangular glass prism .Using proper ray diagram , explain in what way does the direction of the two emergent beams differs with respect to the incident beam of light.

Answer 1

see the diagrams.

In case of a prism the deviation D of the emergent ray from incident ray AB is given by :
                        Mu = sin ((A+D)/2 )  /  sin (A/2)

In case of a glass slab there is no angular deviation. There is a lateral displacement L  of the incident ray thru a slab of thickness t :
                  L = t sin (i - r) / cos r

Answer 2

• Emergent beam of triangular prism is not parallel to its incident beam

• In rectangular glass slab emergent ray is parallel to incident ray.

This is because in rectangular glass slab opposite sides are parallel to each other but in triangular prism sides can be equal but not parallel.