Suppose refractive index μ is given as μ=A+Bλ2 where A and B are constants and λ is wavelength, then dimensions of B are same as that of

As μ= Velocity of light in vaccum  Velocity of light in medium  hence μ is dimensionless. Thus, each term on the RHS of given equation should be dimensionless, i.e., B/λ2 is dimensionless, i.e., B should have dimension of λ2, i.e., m2, i.e., area.