, how many photons of light must strike photosystem II to generate the ATP necessary to produce one glucose molecule in the Calvin cycle?

Four

Explanation:

Four photons are sufficient to generate one glucose molecule and necessary ATP. In photosystem II, a photon initiates the process of photosynthesis after the splitting of water molecule and then travels it through the electron transport chain thereby pumping hydrogen ion. An electrochemical gradient is formed which allows ions to flow from thylakoid into the stroma and generate ATP and sugar molecule. A second photon is then absorbed in the photosystem I to form NADPH molecule which provides energy for Calvin cycle.