Role of Sunlight in Photosynthesis

Light consists of small particles or packages of energy called photons. A single photon is also called quantum.

Chlorophyll molecules absorb light energy and get into an excited state and lose an electron to the outer orbit. No substance can remain in an excited state for long, so the energised and excited chlorophyll molecule comes down to a low energy state known as ground state and releases the extra amount of energy. This energy can be lost as heat, or as light (fluorescence) or can do some work. In photosynthesis, it works by splitting water molecule to produce H⁺ and OH^– ions.

Carotene is orange-yellow pigment present along with chlorophylls in the thylakoid membrane. A carotene molecule breaks down into the vitamin A molecules. It is this pigment which gives carrot its colour.