Provide definitions/explanations for the following terms:
$(1)$ Photosynthesis
$(2)$ Light reaction

(N/A) $(1)$ Photosynthesis: It is the process by which green plants synthesize energy-rich organic compounds (glucose) from low-energy inorganic substances like $CO_2$ and $H_2O$ in the presence of sunlight and chlorophyll.
$(2)$ Light reaction: It is the first phase of photosynthesis that occurs in the thylakoid membranes of chloroplasts. This phase is light-dependent and involves the absorption of light energy to produce $ATP$ and $NADPH$,which are essential for the subsequent biosynthetic phase.