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Investigation on How the Amount of Light Affects Photosynthesis.

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Investigation on How the Amount of Light Affects Photosynthesis Aim In this investigation I hope to find out how the amount of light affects photosynthesis. Plan Photosynthesis occurs only in the presence of light, and takes place in the chloroplasts of green plant cells. Photosynthesis can be defined as the production of simple sugars from carbon dioxide and water causing the release of sugar and oxygen. The fact that all plants need light in order to photosynthesise has been proven many times in experiments, and so it is possible to say that without light, the plant would die. I am saying this because in photosynthesis the carbon dioxide and water convert, using light energy, to form glucose and oxygen. Chlorophyll, which is the green pigment present in the chloroplasts, stores the carbon dioxide and the light energy allows the process to happen Before I start my plan I would like to indicate that all green plants make food by the process of photosynthesis. This can be summarised by the following equation: Carbon Dioxide + Water Glucose + Oxygen 6CO2 (g) + 6H2O (l) C6H12O6 (aq) + 6O2 (g) The carbon dioxide comes from the respiration of plant cells and also forms the air and water around them. Chlorophyll, the green pigment present in the chloroplasts, is the catalyst for the process which absorbs the light. There are many factors, which affect the rate of photosynthesis, including light intensity, temperature and carbon dioxide concentration. > Carbon dioxide concentration - This can affect the rate of photosynthesis, since if there is too little CO2, it can become the limiting factor, thus slowing down the capability of the experiment. ...read more.


Number of bubbles in beaker Distance (cm) Test 1 Test 2 Test 3 Average 5 200 201 200 200 10 183 182 181 182 15 158 163 162 161 20 138 137 137 137 25 117 118 124 120 30 101 102 105 103 Note: some numbers have been rounded up Number of bubbles in beaker Distance (cm) Test 1 Test 2 Test 3 Average 5 184 183 182 183 10 170 169 169 170 15 155 155 155 155 20 137 137 138 138 25 127 130 132 130 30 114 116 118 116 Note: some numbers have been rounded up As you can see from the two tables that I was correct about that anomalous result being wrong. However because these two new tables follow a different pattern (as you can see from the graph) I am not going to be able to change the anomalous in my table. From the pattern on the graph you can see that these tables show that apart from the incorrect result, the rest of my results are fine and follow the same pattern. This was because of my plan as I made sure that all the measurements were correct. For example, I made sure that the lamp was away from the beaker at the measurement it should be. Conclusion During this investigation I found out that the further away you move the lamp the slower the process of photosynthesis occurs. This is due to the fact that the light energy from the bulb cannot reach the plant so then the glucose and oxygen will not be produced as quickly because Photosynthesis is the chemical process, which takes place in every green plant to produce food in the form of glucose. ...read more.


I therefore ensured that in each case I started the stopwatch just after a bubble had been produced, thus heightening the accuracy. Overall, I felt that due to the small volumes of oxygen involved, my experiment was not as accurate as it could have been, however I believe it was accurate enough to support and justify my hypotheses. Improvements could have been made as I have stated, mainly by simply increasing the time taken. However, due to practical time constraints in taking the readings for my investigation, and some consequential problems relating to time extension, I could not in fact make these adjustments. The other obvious way of increasing the reliability of my results would be to take many repeat readings and find an average. From my graph you can see that there is a fairly good correlation and also there are two obvious anomalies, telling us that something must have gone wrong during the experiment. This could have been because of the reasons stated above or because I might have counted too much or too less while the clock was running. Also, from my graph you can see that the results are correct as they follow the same pattern of other student's results. To extend my enquiries into the rate of photosynthesis, I could perhaps try to link in some of the other limiting factors to the same experiment, as well as investigating them in their own right. It could also be interesting to explore the effects of coloured lights on the rate of photosynthesis, which could lead to the question of whether or not other types of light, such as fluorescent lights or halogen lights, would have a different effect on the rate of photosynthesis. ...read more.

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