Normal shift is the apparent shift in the position of an object placed in one medium and viewed along the normal, from the other medium.
Normal shift and apparent shift
When the object and the observer are in two different media, the image of the object appears like shifted from the original position, and it is called a normal shift. The normal shift depends on
- the thickness of the refracting medium and
- its refractive index.
The Apparent shift of the ray is the perpendicular distance between the incident and the emergent ray with reference to the refraction of light through a glass slab.