In an experiment, Rakesh used an equilateral triangular glass prism and projected a narrow beam of white light source from one side of the surface of the prism. He placed a screen on the other side and saw many colours appearing as patches on the screen. But when he placed a second identical prism in an inverted position with respect to the first prism, he found a beam of white light emerging out from the other side of the second prism.
Why did the white light split into its constituent colours after passing through the first prism?