Final answer:
When light strikes the photosystems, electrons are excited and passed down the electron transport chain, which leads to ATP and NADPH production for the Calvin cycle.
Step-by-step explanation:
When light strikes the photosystems during the process of photosynthesis, it excites electrons to a higher energy state. These electrons then move down the electron transport chain. In photosystem II (PSII), light energy is converted into chemical energy by exciting electrons in pigments and transferring them to the chlorophyll molecules, which then pass the excited electrons to the electron transport chain.
This process ultimately leads to the production of ATP and NADPH, which power the Calvin cycle to produce glucose. The initial source of electrons for the chloroplast electron transport chain is water, which is split during the process, releasing electrons to begin their journey through the chain.
When light strikes the photosystems, it excites the electrons and they move out of the photosystems to a higher energy state and then move down the electron transport chain.