The Spectrum, Human Eye Response Light is a form of energy. Virtually all the energy you use on a daily basis began as sunlight energy striking the earth.
Plants capture and store some the sun's energy and convert it into chemical energy.
Later, you use that energy as food or fuel. The rest of the sun's energy heats the earth's surface, air and oceans. With the aid of a glass prism you can demonstrate that the white light coming from the sun is actually made up of many different colors as shown in Figure 1a . Some of the light falls into the visible portion of the spectrum while wavelengths, such as the infrared and ultraviolet rays, remain invisible. The human eye responds to light according to the curve shown on Figure 1b .