The equation of refraction at a spherical surface is

μ₂ / v – μ₁ /u = μ_2- μ₁ /R

taking R=∞, show that this equation leads to equation

real depth/ apparent depth = μ₂/μ₁

when R is infinite, u r talking abt a glass slab.So,u were correct

when R=infinity,ur actually talking abt a plane interface like in the case of slabs.

(n₂/v)-(n₁/u)=0

n₂/v=n₁/u

u/v=n₁/n₂

as mentioned earlier that a surface with infinite radius will act as a plane interface,'u' corresponds to real depth(object distance) and 'v' corresponds to apparent depth(image distance).Furthur something by infinity is 0.Now check out ur statement.