The splitting up of a ray of light of mixed wavelengths by refraction into its components. Dispersion occurs because the deviation for each wavelength is different on account of the different speeds at which waves of different wavelengths pass through the refracting medium. If a ray of white light strikes one face of a prism and passes out of another face, the white light will be split into its components and the full visible spectrum will be formed. The dispersive power of a prism (or other medium) for white light is defined by (nb − nr)/(ny − 1), where nb, nr, and ny are the refractive indices for blue, red, and yellow light respectively. The term is sometimes applied to the separation of wavelengths produced by a diffraction grating.
(nb − nr)/(ny − 1),
Subjects: Science and Mathematics.