Chlorophyll and light react with each other during photosynthesis to provide energy for the plant. Plants take in carbon dioxide from the air and water from the soil and convert them into energy.
When light strikes a plant, it excites the chlorophyll molecule, which is found in a structure called a chloroplast. The chlorophyll molecule then gives up an electron and becomes a cation. This means that it is no longer neutral but has a positive charge.
When the chlorophyll molecule loses an electron, it is then free to take electrons from water. This basically destroys the water molecule, which releases oxygen and hydrogen as it decomposes. This, in turn, allows the plant to use the free hydrogen to turn carbon dioxide into simple sugar. The oxygen is given off as a waste product.
Photosynthesis mostly takes place in the mesophyll, or middle layer, of the plant's leaves.
Light is also necessary for a plant to produce chlorophyll in the first place. This is why most plants that grow in the sun are green: Chlorophyll is a green pigment. The red and blue light found in chlorophyll, but unseen by the human eye, are the colors that actually do the work of photosynthesis.