The dependence of the refractive index of a substance on the frequency of light waves is called: interference diffraction dispersion

The dependence of the refractive index of a substance on the frequency of light waves is called dispersion. Dispersion occurs when different wavelengths (or colors) of light travel at different speeds in a medium, causing them to refract by different amounts. This results in the separation of white light into its constituent colors, as seen in a rainbow or when passing light through a prism.