A narrow beam PQ of white light is passing through a glass prism ABC as shown in the diagram
(i) Write the name and cause of the phenomenon observed.
(ii) Where else in nature is this phenomenon observed ?
(iii) Based on this observation, state the conclusion which can be drawn about the constituents of white light.

Explanation

(i) The phenomenon of splitting of white light into seven colours on passing through a glass-prism is called dispersion of light. The dispersion of white light occurs because colours of white light travel at different speeds through the glass prism.
(ii) Formation of rainbow is an example of dispersion of white light in nature.
(iii) The formation of spectrum of seven colours shows that white light is made up of lights of seven different colours mixed together. That is, white lgiht is a mixture of seven colours ( or seven coloured lights ) , i.e., red, orange ,yellow , green, blue , indigo and violet.