A light ray enters from medium A to medium B as shown in Figure 10.2. The refractive index of medium B relative to A will be

As it is clear from the figure, when the light rays travelled from medium A to medium B, then they bend towards the normal which means that medium B has higher refractive index and less speed of light with respect to medium A. So, refractive index of medium B with respect to medium A will be greater than unity.