text: Part of energy is always used to increase the entropy of the universe as per laws of thermodynamics. Any photon when is absorbed electrons in the pigment that absorbs the photon are energized/ excited. These excited electrons come to the ground level by 1. transferring their energy to other carrier so that ATP is generated. 2. give out the energy as heat energy so that the temperature increases. 3. give out a photon with less energy content i. e. emit light of longer wavelength. It is called fluorescence. What happens depends upon the system.