The absolute refractive indices of glass and water are 3/2 and 4/3 respectively. What is the refractive index of glass with respect to water?

1. The refractive index of glass with respect to water is $^{water}n_{glass} = \dfrac{n_{glass}}{n_{water}}$. 2. Substitute the absolute indices: $^{water}n_{glass} = \dfrac{3/2}{4/3}$. 3. Divide the fractions: $\dfrac{3}{2} \times \dfrac{3}{4} = \dfrac{9}{8}$. 4. The value 8/9 is the reciprocal (water with respect to glass); 2 multiplies the indices instead of dividing. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 6 "Refraction of Light", p.88_