Refractive Index

A diamond $(\mathrm{n} = 2.42)$ is dipped in a liquid of refractive index $1.4$. Find the refractive index of diamond with respect to the liquid.

Find the refractive index of air with respect to water $(n_{\mathrm{water}}=4/3)$

A ray of light travelling in air falls on the surface of a transparent material at an angle of $45°$ to the normal. It bends by $15°$ after refraction. Find the refractive index of the material.

The refractive indices of water and glass are $4/3$ and $3/2$ respectively. Find the speed of light in each.

Define refractive index.