When a beam of white light is passed through a prism, it splits to form lights of seven colours. Is it possible to recombine the lights of seven colours to obtain the white light again? Explain your answer.

Yes it is possible to obtain the white color from the recombination of the seven colors which are obtained by dispersion of light by prism. Figure below shows the set up for the same.

We take two glass prism and place the second one upside down w.r.t to the first one The first prism splits the white light into seven colors. When these colors fall on the inverted prism, it recombines all the colors into white light which is observed ultimately as a patch of white light on the screen.