What is recombination prism.?Explain very briefly.

 Take two glass prisms P1 and P2 and place the second prism P2 upside down with respect to the first prism P1. Now, allow a beam of white light to fall on first prism P1. 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.