A student investigates the effect of light intensity on the rate of photosynthesis in pondweed.
He places a lamp at different distances from the pondweed and counts the bubbles of gas given off.
Give two reasons why counting bubbles is not an accurate way of measuring the volume of gas given off.
Suggest a piece of apparatus the student could use to measure the volume of gas more accurately.
The light intensity at 10 cm from the lamp is 64 arbitrary units.
Light intensity is inversely proportional to the square of the distance from the lamp.
Calculate the light intensity at 40 cm from the lamp.
The lamp also gives out heat.
Explain why this could make the results invalid, and suggest how the student could stop this happening.
117 exam-style questions on OCR GCSE Biology 1.4 Photosynthesis, covering 1.4.1 Photosynthesisers as biomass producers, 1.4.2 Factors affecting the rate of photosynthesis, and 1.4.3 Limiting factors in photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.