White light is a mixture of colours rather thana single colour. and a prism refracts these different colours by different amounts. This effect is called dispersion, and the colour range produced is known as a spectnun. The spectrum consists of seven colours:- red. orange. yellow. green. blue. indigo and violet.

The angles of refraction for the different colours are not the same. Red is refracted the least because it has the largest wavelength and violet is refracted the most because it has the smallest wavelength.

Colour vision.

If red, green and blue light fall together on a white screen the screen appears white. The retina of the human eye only contains three main types of colour-sensitive cells. These respond to red, green and blue. White light stimulates all three. You experience all colours by the extent to which the three types of colour-sensitive cells are stimulated. Colour TV makes use of this principle.