An experiment into the effect of wavelength of light on the rate of photosynthesis was carried out using algae and an indicator - Scottish Highers Biology - Question 19 - 2023

To ensure the validity of the experiment, it's crucial to minimize the influence of external temperature on the algae. By placing a heat shield between the light source and the bottle, we prevent excess heat from affecting the water temperature in the bottle. This ensures that any observed change in the color of the indicator is primarily due to the effects of light wavelength on photosynthesis, rather than heat-induced reactions.