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.