The refractive index of lens flint glass is 1.65 and for alcohol, it is 1.36 with respect to air, then the refractive index of the dens flint glass with respect to alcohol is
Refractive index of air, μair = 1;
Given;
Refractive index of flint glass w.r.t air, airμglass = 1.65;
Refractive index of alcohol w.r.t air, airμalcohol = 1.36;
Refractive index of flint glass w.r.t alcohol = alcoholμglass = airμglass / airμalcohol =
⇒ alcoholμglass = 1.213
Hence the refractive index of flint glass w.r.t alcohol is 1.213.