This is from my Physics practical experiments. The experiment is to find the refractive power of the prism for different colours and also to determine the dispersive power of the material of the prism. My question is how does the refractive index of the material of the prism vary with the wavelength of the source light used? The answer is the refractive index decreases with the increase in the wavelength of the light. I do not want the equation of the relation but the physical significance of the relation.