Who discovered that light is essential for releasing oxygen in plants?

$..............$ provided evidence for the production of glucose when plants grow. Glucose is usually stored as starch.

The discovery that the first stable product of $CO_2$ fixation in photosynthesis is $3$-phosphoglyceric acid $(PGA)$ was made by whom?

Variegated leaves of a plant were supplied with radioactive carbon dioxide $(^{14}CO_2)$ during an experiment. Leaf $X$ was kept in the dark and leaf $Y$ was kept in the light. At the end of the experiment,the radioactivity in the leaves was measured and found to be as shown in the diagram. What is the most likely explanation for the level of radioactivity found in the yellow zone of leaf $Y$?

Which is the evidence to show that $O_2$ released in photosynthesis comes from water?

Which isotope is used to study photosynthesis?