For two MAIN IDEA: The index of refraction, n, of a medium is equal to the ratio of the wavelength of light in a vacuum, A,, to the wavelength of light in the medium, A, n= different media, m === The frequency of light remains the same in all media 5. A ray of light with a wavelength of 540 nm goes from air into zircon. What is the wavelength in zircon? The index of refraction for zircon is 1.92.