A beam of white light, as from the sun, strikes a prism made of flint glass. Flint glass has a high refractive index and a high dispersion (spread). Shorter wavelengths (blue) are refracted more than the longer wavelengths (red), causing the beam to split into a rainbow or spectrum. This simulation uses real refractive indices to calculate the refraction of each colour. Most graphics of this subject increase the dispersion for clarity. This still graphic was distilled from the matching animation that shows the coloured beams in sequence.