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An Investigation on the Effects of Light Intensity on Photosynthesis

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Plan

I plan to investigate how light intensity affects the rate of photosynthesis in pondweed. The rate of photosynthesis will be measured by the number of bubbles given off (considering that oxygen is produced as a waste gas during photosynthesis). The light intensity is measured by the distance between the lamp and pondweed.

Fair test:

Fix: the amount of pondweed, the amount of water and sodium hydrogen carbonate solution in the test tube, the time allowed for each experiment

Change: the distance from the lamp to the pondweed (light intensity)

Measure: the number of bubbles given off by the pondweed, the temperature of the water bath

Variables:

The following are factors that affect the rate of photosynthesis: …show more content…

This was put in the test tube which is filled with 6ml of water and 6ml of sodium hydrogen carbonate solution. The test tube was put into the water bath so the temperature remained constant. The thermometer was put in the water bath to check that the temperature did stay the same. The clamp and stand was used to keep the test tube upright. The lamp, to begin with, was put 10cm away from the plant (this was measured by the ruler). The plant was left to climatise for 5minutes so the results were more accurate. The stopwatch was started and the bubbles produced by the plant by photosynthesis were counted. After 1minute the number of bubbles were recorded. The temperature was recorded at the beginning and end. This was repeated another two times so that an average of the results could be found. The whole process was done again but the light was 20cm away, then 30cm, 40cm, 50cm and finally 60cm.

Theory:

In order for photosynthesis to happen light is needed. The more sunlight there is then the more the plant will photosynthesise because the light is the input energy put into the process (it is transformed into chemical energy). The reaction is endothermic so light is needed. But there comes a point where more light does not make any difference to the rate of photosynthesis because the light is at the light saturation point and photosynthesis occurs at the same speed even with more light because it has

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