Sunlight is the combination of seven components. When sunlight is allowed to pass through the glass prism it blends and gets split into seven colours. All the seven colour has different wavelength and while entering through a prism it bends (due to refraction) and angle of bending is different for all the colour. And while coming out from the prism light again get bend and we can see the entire different colour. This is also called Dispersion means spreading of white light into its full spectrum.