Refractive index of diamond is 2.5 and that of glass is 1.5. Calculate the refractive index of diamond with respect to glass.

Refractive index of glass, µ_g = 1.5

Refractive index of diamond, µ_d = 2.5

From relative refractive index

${}^{\mathrm{g}}\mathrm{\mu }_{\mathrm{d}}=\frac{{\mathrm{\mu }}_{\mathrm{d}}}{{\mathrm{\mu }}_{\mathrm{g}}}=\frac{2.5}{1.5}=1.667$