Light energy is processed in the light reaction of photosynthesis through an electron transport chain .
In photosynthesis, the light energy is first captured by the light harvesting complex of chloroplast of green leafs and used to split water by the process of photolysis. The process of photolysis causes release of oxygen and electron from water. This resulting electron is then absorbed by the photosystem II located in the chloroplast due to which photosystem II reaches higher energy level. Thenafter, the electron is passed from a series of complexes to photosystem I. Ultimately the electron from photosystem I reaches NAD+ and reduces it to NADH which is further used as energy source in the dark reaction of photosynthesis. This passage of electron from various complexes is known as electron transport chain or electron transport system.