The equation for photosynthesis is 6H2O (water) + 6CO2 (carbon dioxide) + Light Energy → C6H12O6 (glucose) + 6O2 (oxygen). When first discovered, scientists were trying to decide if the oxygen in the product came from carbon dioxide or water. Which statement describes how scientists traced the path of oxygen?

Question

They used a radioactive isotope and tracked it with a Becquerel counter.
They used a radioactive isotope and tracked it with a Geiger counter.
They used a stable isotope and tracked it with a Becquerel counter.
They used a stable isotope and tracked it with a Geiger counter.

Answer 1

The correct statement is:

They used a radioactive isotope and tracked it with a Geiger counter.

Scientists used radioactive isotopes, such as oxygen-18, to trace the pathway of oxygen in the photosynthesis process. The Geiger counter is one instrument used to detect and measure radioactivity, making it suitable for this sort of investigation.