Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics:
Dispersion By a Prism:
The phenomenon of splitting of light into its component colour is known as dispersion.
The pattern of colour components of light is called the spectrum of the sunlight.
When a narrow beam of Sunlight is incident on a glass prism, the emergent light is seen to be consist of seven colours namely violet, Indigo, blue, green, yellow, orange and red.
The rad bends the least, while the violet light bends the most. Because red light is at the long wavelength while violet is at the short wavelength.