Material dispersion is caused by the
∙ a. Wavelength dependence of the index of refraction
∙ b. Wavelength independence of the index of refraction
∙ c. Dependence of the propagation constant on the mode number
∙ d. Independence of the propagation constant on the mode number
∙ a. Wavelength dependence of the index of refraction
∙ b. Wavelength independence of the index of refraction
∙ c. Dependence of the propagation constant on the mode number
∙ d. Independence of the propagation constant on the mode number