Science

A great experiment to prove that light reactions occur prior to carbon fixing is the Hill reaction. This experiment uses the principles of photosynthesis to measure the amount of oxygen produced by the photosynthetic organism in the presence of different light intensities. Scientists measure the amount of oxygen produced in order to determine how much light energy is being converted into chemical energy. Start out by collecting identical samples of the desired photosynthetic organism, such as an alga or a plant. The samples should be grown in identical conditions, such as light, temperature, etc. Once the organisms are ready, place them in a closed chamber and expose them to different light intensities. For example, one part of the chamber may have a bright light shining on it, and the other part may have only a dim light. Measure the amount of oxygen produced in both chambers. The results should show that the chamber with the brighter light produces more oxygen than the chamber with the dim light. This proves that carbon-fixing reactions are preceded by light reactions.