Mixing Light Back Together

If a prism splits white light into rainbow colors, can you put them back together? Yes!

Newton proved this by painting a disc with all the rainbow colors and spinning it fast. When the disc spins, the colors blur together and the disc looks white (or light gray). The spinning combines the colors back into white light!

This proves that white light really is ALL the colors combined. Splitting and recombining: it works both ways.