When a ray of light travels through a glass slab from air, it bends towards the normal and when it comes out of the other side of the glass slab, it bends away from the normal. It is found that the incident ray and the emergent ray are not along the same straight line, but the emergent ray seems to be displaced with respect to the incident ray. This shift in the emergent ray with respect to the incident ray is called lateral shift or lateral displacement. The incident and the emergent rays, however, remain parallel. The diagram is as shown:
