Question
When we place a glass prism in the path of a narrow beam of white light a spectrum is obtained. What happens when a second identical prism is placed in an inverted position with respect to the first prism? Draw a labelled ray diagram to illustrate it.
Solution
The sunlight or white light is dispersed into its seven constituent colors and a spectrum is formed on passing through the first prism. The other inverted prism recombines all the seven colors and gives a white light. 
