Two transparent slabs having equal thickness but different refractive indices μ 1 and μ 2 are pasted side by side to form a composite slab. This slab is placed just after the double slit in a Young’s experiment so that the light from one slit goes through one material and the light from the other slit goes through the other material. What should be the minimum thickness of the slab so that there is a minimum at the point P 0 which is equidistant from the slits?

Question

Philoid · Accepted Answer

Here, in front of each slab we have a slab of different refractive index but equal thickness. Hence, the optical path difference of the waves after passing from the slab would be

Point P₀ is equidistant from both slab. hence, to get a minimum P₀ at the path difference should be

Therefore,