Life Sciences

Energy from Light

When light shines on grass, the grass absorbs the light's energy. This sparks a series of chemical reactions that combine carbon dioxide and water to make food. In this exhibit, when the light in the container is shut off, the carbon dioxide level—as indicated on the screen—rises, because the grass no longer has the energy to absorb it. When the light shines again, the carbon dioxide level drops because it now has the energy to absorb carbon dioxide. Grass and other green plants trap the energy with a pigment called chlorophyll. This pigment allows plants to use that energy to make food from carbon dioxide and water. During this process, called photosynthesis, they also produce oxygen as waste.