A researcher investigated the rate of photosynthesis in the aquatic macrophyte Elodea canadensis. An adjustable LED lamp was placed at various distances, ddd, from a beaker containing the specimen. The relative light intensity, III, received by the plant is inversely proportional to the square of the distance from the lamp:
I∝1d2 I \propto \frac{1}{d^2} I∝d21Calculate the relative light intensity at a distance of d=50 cmd = 50\text{ cm}d=50 cm. Give your answer in standard form with the unit cm−2\text{cm}^{-2}cm−2.
When the distance d d\,d was decreased from 12 cm to 6 cm, the rate of oxygen release by the macrophyte remained completely unchanged despite a fourfold increase in light intensity. Explain why the rate of photosynthesis did not increase in this range.
54 exam-style questions on AQA GCSE Biology 4.1 Photosynthesis, covering 4.1.1 Photosynthetic reaction, 4.1.2 Rate of photosynthesis, and 4.1.3 Uses of glucose from photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.