Describe an activity to show that colours of white light split by a glass prism can be recombined to get white light by another identical glass prism. Also, draw a ray diagram to show the recombination of the spectrum of white light.


1. When a glass prism is placed in the path of a narrow beam of white light, it gets dispersed into its seven constituent colours at different angles. And, all these colours are arranged according to their wavelengths (violet, indigo, blue, green, yellow, orange and red from down to up).

2. Now, a second identical prism is placed in an inverted position with respect to the first prism to obtain a beam of white light, as it recombines the spectrum obtained by the first prism. It happens because the refraction produced by the second prism is equal and opposite to that produced by the first prism.

The ray diagram of recombination of the spectrum of white light is as shown below:


The phenomenon of splitting white light into its components colours (violet, indigo, blue, green, yellow, orange and red) while passing through a prism is known as the Dispersion of light.

The cause of the dispersion of light through the prism is because white light is a mixture of seven different colours and they get refracted (bend) at different angles in the prism medium due to differences in their speed and wavelengths. So they get separated.


Simply Easy Learning

Updated on: 10-Oct-2022


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