1. Light energy excites electrons.2. Water molecules are split.3. NADPH is formed.

Photosystem II is the first to absorb light and excite electrons during the light-dependent reactions. It also replaces lost electrons by splitting water, releasing oxygen and hydrogen ions. Later, light excites electrons in photosystem I, which helps form NADPH. Thus, the sequence is photosystem II, photosystem II, photosystem I.

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