What is a Spectrum? How is It Formed?

Spectrum is a series of energies arranged according to wavelength. It is the series of images produced when a beam of radiant energy is subject to dispersion. A rainbow-coloured band of light is formed when white light is passed through a prism or a diffraction grating. This band of colours results from the fact that the different wavelengths of light are bent in varying degrees by the dispersing medium and is evidence of the fact that white light is composed of coloured light of various wavelengths.