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Investigation into the effect of light intensity on the rate of photosynthesis.

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Ellen John Investigation into the effect of light intensity on the rate of photosynthesis Aim To find out how the amount of light present effects the rate of photosynthesis. Plan Without light plants are unable to photosynthesis this is because they need the light energy from the sun to convert carbon dioxide and water into oxygen and glucose. Carbon dioxide + water + light energy oxygen + glucose I am going to investigate how one of the variables, in this case light, effects the rate of photosynthesis .To carry out the experiment the equipment I will need is a beaker, test tube, lamp and long ruler. Firstly fill the beaker with water and the test tube then place the pondweed (elodea) into the test tube and add some sodium hydrogen carbonate, this helps the level of carbon dioxide to stay constant so carbon dioxide does not become a limiting factor. ...read more.


This will be done by measuring the temperature of the water in the beaker to make sure it is not increasing it is important that the temperature is kept constant as it affects the rate at which the plant will photosynthesis therefore if it changes then the experiment would not be fair, if at anytime it does then more cold water will be added. NaHCO3 will be added to keep the level of carbon dioxide fairly constant. Results Distance of light from plant O bubbles counted/min 1 2 3 Average Bubbles/min 1000 distance2 (light intensity) 5 44 40 39 41 40 10 17 19 20 18.7 10 15 2 2 2 2 4.4 20 1 2 1 1.3 2.5 25 0 0 0 0 1.6 30 0 0 0 0 1.1 Conclusion The results show that the amount of bubbles decrease as the light intensity decreases showing that there is less photosynthesis taking place. ...read more.


Though the results taken for when the distance of the light is 5cm from the beaker there is quite a varied amount of bubbles counted in the three readings. This is most likely to be due to human error, someone miss counting the bubbles. A more reliable way to measure the rate of the photosynthesis would of be to measure the amount of oxygen being produced by attaching a syringe to the test tube, this would suck the air into a capillary tube, you can then measure more accurately the amount of oxygen being produced by measuring the air bubble in the capillary tube rather than counting the bubbles produced each minute. To improve the second graph I would take another reading after the light intensity passed 40 to see if the amount of bubbles being produced would carry on increasing at the same rate or would slow down. I think the results obtained are sufficiently accurate to support my conclusion as the results prove what I have said. ...read more.

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