Newton made a hole in a piece of wood where a thin ray of white light could pass through. He let this ray of light pass through a prism (a triangular piece of glass) onto a white sheet of paper. After passing through the prism, the white light split into 7 colors – ROYGBIV (red, orange, yellow, green, blue, indigo, and violet). Newton then used a second prism to turn the refracted light (with seven colors) into white light again. Newton concluded that white light is composed of 7 colors.
Before Newton’s experiment, people thought that colors appear when white light becomes “contaminated” after passing through a material. Newton’s experiment proved that light does not simply reveal an object’s color, but that it is actually light that gives color to an object. With his experiments, Newton discovered that an object’s color depends on how much light it absorbs or reflects.