Explanation:

Photolysis:
Photolysis is the process in which a molecule is broken down into smaller components by absorbing light energy. In the case of oxygen evolution, water molecules are photolyzed to release oxygen gas.

Photolysis of Water:
During the process of photosynthesis, when light energy is absorbed by chlorophyll molecules, it excites electrons. These excited electrons are used to convert carbon dioxide and water into glucose and oxygen. In this process, water molecules are photolyzed to release oxygen gas.

Equation:
The overall equation for the photolysis of water is:

2H2O -> 4H+ + 4e- + O2

This equation shows that for every two molecules of water that are photolyzed, four protons (H+) and four electrons (e-) are released, along with one molecule of oxygen gas (O2).

Number of Electrons Released:
According to the equation, for every two molecules of water photolyzed, four electrons are released. This means that for one molecule of oxygen evolved, two water molecules must be photolyzed. Therefore, the number of electrons released during photolysis when one molecule of oxygen is evolved is four.

Summary:
- Photolysis is the process in which a molecule is broken down into smaller components by absorbing light energy.
- During photosynthesis, water molecules are photolyzed to release oxygen gas.
- The equation for the photolysis of water shows that for every two molecules of water photolyzed, four electrons are released along with one molecule of oxygen gas.
- Therefore, the number of electrons released during photolysis when one molecule of oxygen is evolved is four.