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Question
Describe an activity to show that the colours of white light splitted 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.
Solution
The phenomenon of dispersion of white light through a prism and then its recombination can be explained with the help of two identical glass prisms. For this to happen, white light is made to made to fall on the surface of the prism. Since different colours of white light have different wavelengths, the amount of bending of light is different. Red light bends the least and violet light bends the most. So, we obtain a spectrum of seven colours, with violet light at the bottom and red at the top. This spectrum is then made to fall on an indentical prism, which is kept inverted. When the spectrum passes through the prism, all the colours bend once again, resulting in their recombination (as shown in the figure below). Hence, the light coming out of the second prism will be white.
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