# Rates of Photosynthesis

### GCSE Biology Required Practical - Photosynthesis Experiment

Investigate the effect of light intensity on the rate of photosynthesis.

• Pondweeds (Algal balls or similar) must be set up and placed at varying distances from a light source to investigate the effect of light intensity on the rate of photosynthesis.
• The rate must be measured and compared to the distance away from the light source.

Rates Of Photosynthesis
How to measure the rate of photosynthesis of pondweed?

00:00 Preparing the sample
02:34 Changing light intensity
04:21 Counting bubbles
05:11 Analysing data
05:23 Alternative method - volume of collected gas

Required Practical: Photosynthesis

1. How to investigate the effect of light intensity of the rate of photosynthesis in a pondweed.
2. Explain how the results of this are affected by the inverse-square law. (Higher Tier)

Check out the sample question and solution on Sample Assessment Material (page 33), paper 1BI0/1BH and 1BIO/1BF.

A scientist investigates the effect of light intensity on photosynthesis.
He sets up the equipment shown in figure 1.
He places the lamp 10cm from the test tube and records the numbre of bubbles produced in five minutes.
He repeats the procedure with the lamp at a distance of 20cm and 30cm away from the test tube.
The scientist wants to repeat his investigation at each distance. State three variables that should be kept constant to improve the results.

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