Explain dispersive and non-dispersive medium.

(N/A) medium is called $dispersive$ if the refractive index of the medium depends on the wavelength of light. In such a medium,different colors (wavelengths) travel at different speeds,causing light to disperse into its constituent colors.
$A$ medium is called $non-dispersive$ if the refractive index of the medium is independent of the wavelength of light. In such a medium,all colors travel at the same speed.
$1$. $Non-dispersive$ medium: Vacuum (or air,approximately) is a $non-dispersive$ medium. This is why sunlight reaches us as white light rather than separated colors.
$2$. $Dispersive$ medium: Glass or water are examples of $dispersive$ media,as they cause the separation of white light into its spectrum (dispersion).