The image of an object kept at a distance of 30 cm in front of a concave mirror is found to coincide with itself. If a glass slab `(mu=1.5)` of thickness 3 cm is introduced between the mirror and the object, then
a. Identify, in which direction the mirror should be displaced so that the final image may again coincide with the object itself.
b. Find the magnitude of displacement.

Explanation

a. Since the apparent shift occurs in the direction of incident light, therefore the mirror should be displaced away from the object.

b. The magnitude of displacement is equal to the apparent shift. i.e.,
`s=t(1-(1)/(mu))=3(1-(1)/(3//2))=1cm`