Question

The absolute refractive index of water is 4/3.what is the refractive index of water relative to glass?

Answer 1

Absolute refractive index of water = 4/3
Absolute refractive index of glass = 3/2

refractive index of water relative to glass = Absolute refractive index of water / Absolute refractive index of glass 

⇒ refractive index of water relative to glass = $\frac{4/3}{3/2} = \frac{4 \times 2}{3 \times 3} = \frac{8}{9}$

Answer 2

Relative refractive index of glass to water=9/8

Refreactive index of water relative to glass = 1/(9/8)=8/9