When does photovoltaic action occur?

Photovoltaic action occurs when light photons hit a semiconductor material, causing electrons to be knocked loose from their atoms. This process essentially generates a flow of electricity as the electrons become excited and move about, particularly in materials like silicon used in solar cells. The interaction of photons with the semiconductor creates electron-hole pairs—the electrons that were knocked loose can flow through the material, creating an electric current.

The choice that mentions electrons striking one of two connected plates aligns with this description. In photovoltaic cells, these connected plates are part of the overall circuit setup that enables the flow of electricity when the electrons are mobilized. This principle underlies the conversion of solar energy into electrical energy.

In contrast, the other options do not accurately describe photovoltaic action. Converting light to heat does not involve the generation of electrical energy. The collision of photons with air does not create a flow of electrons. Movement of ions through a conductor is related to electrolytic processes rather than the photovoltaic effect. Thus, the correct choice reflects the fundamental principle of how photovoltaic cells convert light into usable electrical energy.