The phenomenon of splitting of white light into its seven constituent colours, when it passes through a glass prism, is called the dispersion of light.When a beam of white light enters a prism, it gets refracted at point and splits into its seven constituent colours i.e., violet, indigo, blue, green, yellow, orange and red i.e., VIBGYOR. This splitting of light rays occurs because of the different angles of bending for each colour and this different angles of bending occurs because different components of light have different refractive indices or speed of different colours is different in glass when passing through the glass prism. When a beam of sunlight is allowed to fall on one of the rectangular surfaces of the glass prism, we obtain a coloured spectrum with red and violet colour at its extremes.