Effect of light intensity on photosynthesis

• What is the aim for this practical?

  To investigate how light intensity affects the rate of photosynthesis.
• The steps:

  • Place pondweed (e.g., Elodea) in a test tube of water.
  • Shine a lamp at different distances (e.g., 10cm, 20cm, 30cm).
  • Count the number of oxygen bubbles released in 1 minute.
  • Repeat and calculate averages.
• What is the independent variable?

  Light intensity (distance of lamp).
• What is the dependent variable?

  Number of bubbles.
• What is the control variable?

  Pondweed type, CO₂ levels, temperature.