After his experience with planetary motion, Isaac Newton grew interested in optics, the branch of science dealing with the behavior of light. In his first experiment, Isaac darkened his room and made a circular hole in the window shutters of his room. Then he placed a prism in the path of the sunbeam, which caused the light to refract against the wall that was opposite the window shutters. The colors always appeared in the same order on the wall - red, orange, yellow, green, blue, indigo and violet. The colors were in a rectangular shape although the hole in the window shutter was in the shape of a circle. Isaac concluded that the prism bent the colors. It bent the red light the least and the blue light the most.

After the first experiment, he tried another experiment using two prisms. This time, he placed another prism upside-down in front of the first prism. The result this time was a circle of white light on the wall.

For his third experiment, Newton used a card with a hole in it, which he held between two triangular prisms. Only the red light passed through the hole. Isaac repeated this experiment with other colors: orange, yellow, green, blue, indigo, and violet. The isolated color was the only color that showed on the wall.

Newton concluded from the three experiments that light rays are made up of tiny particles. He learned from his first experiment that white light is made up of the seven colors of the rainbow - red, orange, yellow, green, blue, indigo, and purple.