Final answer:
The light reactions of photosynthesis produce ATP and NADPH, which are used in the Calvin cycle to synthesize carbohydrates, and they also release oxygen as a byproduct.
Step-by-step explanation:
The overall outcome of the light reactions in photosynthesis is the production of chemical energy in the forms of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate) as well as the release of oxygen as a byproduct. The light reactions take place within the thylakoid membranes of chloroplasts. Here, light energy is captured by chlorophyll and other pigments and used to split water molecules into oxygen, protons, and electrons. The oxygen is released into the atmosphere, while the electrons move through a series of reactions to produce ATP and NADPH. These energy-rich molecules are then used in the Calvin cycle, also known as the light-independent reactions, to synthesize carbohydrates from carbon dioxide.