This page needs JavaScript to draw the scene. In words: sunlight is a stream of photons of many wavelengths. A prism bends violet more than red, so white light fans into colours. A photon's energy is E = hc / λ, so shorter waves carry more energy. Chlorophyll in a leaf catches red and blue light well and green poorly, so more green bounces back and the leaf looks green. A caught photon's energy hops from chlorophyll to chlorophyll to the reaction centre P680, which sends out an electron; water is split to replace it and oxygen is released.