A technician uses a lamp to investigate photosynthesis in a tray of young cress plants. Light intensity is the limiting factor when the lamp is 45 cm from the plants.
At this distance, the plants take up 24 mg of carbon dioxide in 8 minutes8\ \text{minutes}8 minutes.
The lamp is moved to 15 cm from the plants for 6 minutes6\ \text{minutes}6 minutes. The temperature and carbon dioxide concentration are kept constant. Other measurements under these conditions show that the rate of carbon dioxide uptake cannot rise above 8.0 mg per minute8.0\ \text{mg per minute}8.0 mg per minute.
Calculate the mass of carbon dioxide expected to be taken up by the plants during the 6 minutes6\ \text{minutes}6 minutes.
87 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.