As it approaches the convective zone, all the photons have been absorbed and the energy is now transported by convection. The Convective Zone is a region where that gas physically moves up and down. In the radiative zone, there was little or no movement for energy transport. But now, all of it is for energy transport. This movement of gas takes on the form of convective cells.
Hotter gas rises while cooler gas descends.
The density drops abruptly at the top of the convective zone allowing radiation to transport the energy once again. The photosphere where this energy is emitted in the form of light give the sun a very sharp-edged appearance since it is so thin. Below the density is too high, above too low. The tops of the uppermost convection cells descriged above can be seen just below the photosphere and are collectively called Granulation. Simillarly, astronomers have detected much larger structures with similar characteristics.