(a) Photosynthesis is a complex process involving a light dependent stage and a light independent stage. A student carried out an experiment to investigate the effect of light intensity and light wavelength on the rate of photosynthesis. • An aquatic plant, Elodea canadensis, was put into a beaker containing sodium hydrogencarbonate solution as a source of carbon dioxide. • To minimise changes in temperature, an LED lamp was used as a source of light. • The lamp was switched on and the number of bubbles released by the aquatic plant in 1 minute was counted. • The lamp was placed at seven different distances from the beaker to change light intensity. • Five replicates were carried out at each lamp distance. • All other variables were controlled. (b) The student calculated the light intensity for each distance (d) using 1/d² . Table 5.1 shows the calculated light intensities for each distance. distance between plant and lamp/m | light intensity/1/d² ---|--- 0.025 | 1600 0.050 | 400 0.100 | 0.150 | 44 0.200 | 25 0.250 | 16 0.300 | 11 (c) At each distance from the lamp, the experiment was repeated using a red filter in front of the lamp to give a different wavelength of light. The experiment was repeated using a blue filter and then using a green filter. Each filter transmitted the same light intensity. The student calculated the mean rate of bubble production as a measure of the rate of photosynthesis. Fig. 5.1 shows a graph of the results. [Figure 5.1]