How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

By using two identical prisms, one placed inverted with respect to the other we get a narrow beam of white light incident on one prism emerges out of the second prism as white light.

Explanation

1. When a glass prism is placed in the path of a narrow beam of white light, it gets dispersed into its seven constituent colors at different angles. And, all these colors 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.