Yes, it is possible to recombine the lights of seven colours to obtain the white light again by placing another similar prism alongside the first one in the inverted position as shown below. The first prism disperses the white light into seven coloured rays. the second prism receives all the seven coloured rays from the first prism and recombines them into original white light. This is because the refration produced by the second prism is equal and opposite to that produced by the first prism.
