Dispersion of White Light
When white light is refracted by a glass prism, it is refracted at the air-glass interface as it enters, and again as it leaves the prism. White light is made up of many different wavelengths, each wavelength corresponding to a different colour. The amount by which a ray is refracted depends on the wavelength. Red light - the longest wavelength of visible light - is refracted the least, and violet light - the shortest wavelength - is refracted the most.White light refracted into many different colours is said to have been dispersed, and light so dispersed can be reformed into white light by an appropriately placed prism.