Question

state the condition under which the lateral displacement in a glass slab is zero

Answer 1

When the light ray is incident normally on a glass slab.

Answer 2

It could be possible if the ray of light enters the glass slab from the medium which has the same density as the glass slab. Because there will be no change the path light ray and it would travel a straight path. Hence, the lateral displacement will be zero.

Hope this helps you.