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.

(N/A) To obtain a beam of white light from a narrow beam of white light after passing through two prisms,the two identical prisms must be placed in an inverted position with respect to each other.
When a beam of white light enters the first prism $(P_1)$,it undergoes dispersion and splits into its constituent seven colors.
When these dispersed rays fall on the second prism $(P_2)$,which is placed in an inverted position,it recombines the colors to form a beam of white light that emerges from the second prism.