Final answer:
When light strikes chlorophyll, it energizes electrons and causes them to become excited. These excited electrons are passed along a pathway, and in the process, a water molecule is split to release an electron. This splitting of water produces oxygen and hydrogen ions.
Step-by-step explanation:
When light strikes chlorophyll in the chloroplast, it energizes electrons within the molecule, causing them to jump up to higher energy levels and become excited. These excited electrons are then passed along a pathway to other chlorophyll molecules. In the process, a molecule of water is split to release an electron, which replaces the one donated by the chlorophyll. This splitting of water results in the formation of oxygen and hydrogen ions in the thylakoid space.