Newton used Newton's color wheel to discover the composition of light. Newton described this scene in his book The New Theory of Light and Color: "I made a triangular glass prism at the beginning of 1666, and used it to study the phenomenon of color. To this end, I darkened the room, punched a small hole in the window to let in a proper amount of sunlight, and put a prism at the entrance of light to refract the light energy passing through the prism to the opposite wall. When I first saw the bright and strong colors it produced, I felt great pleasure. "
We can repeat Newton's experiment in the laboratory, and you will see the sunlight refracted through the prism to form a colored light band on the screen. One end of the light band near the top corner of the prism is red, and the other end near the bottom is purple, forming seven-color light bands of red, orange, yellow, green, cyan, blue and purple. If you put another prism, turn its bottom upside down and let seven colors of light pass through, then it will be a beam of white light. Newton's experiments show that white light is a mixture of seven colors of light, and it is the sun that brings us color.
Because what we see is the superposition of all colors of light. Seven colors of light add up to white. In fact, there are only three primary colors in optics, red, green and blue. These three colors can be mixed according to the principle of additive method and can be expressed by color equation:
Red+green = yellow; Green+blue = green; Red+blue = purple; Red+green+blue = white.