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Investigate the affect of light colour (wavelength) on photosynthesis.

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GCSE Biology Coursework Year 11 Craig Lochhead Aim To investigate the affect of light colour (wavelength) on photosynthesis. Prediction Photosynthesis is the process by which plants use the energy from sunlight to produce glucose. Using chlorophyll, water and sunlight, the plant produces food (glucose) for itself and oxygen as a waste gas, which we breathe. This reaction is shown below. (Sunlight) 6H20 + 6CO2 --> C6H1206 + 6O2 (Chlorophyll) Photosynthesis occurs in a leaf of a plant. The raw materials of photosynthesis, water and carbon dioxide, enter the cells of the leaf, and the products of photosynthesis, sugar and oxygen, leave the leaf. The more light there is to be absorbed by the plant, the more oxygen there is released by the plant. Therefore we can measure the rate of photosynthesis by collecting the oxygen bubbles released by the plant. The plant itself will be put in water so that the bubbles can be measured, using a micro burette. The factors that can affect the rate of photosynthesis are sunlight, water and carbon dioxide as these are all raw materials for photosynthesis. In this experiment the factor that I will change is the different wavelength of sunlight. I would have done it by using different coloured filters to change the white colour to any other colour of my choice. I will use the colours white (as a control), orange, blue, green, yellow and red. ...read more.


The micro burette will be placed for 1 minute each test and we will measure how much oxygen is released from the plant. This will be done three times. This is done to see if all the measurements were done fairly and accurate. Also this was done three times to find a good average so that a good graph can be drawn. Another reason why a graph is drawn is because it makes it easier to spot anomalous results. After testing for white light there is other colour lights that can be tested such as orange, blue, green yellow and red. To test the other different colours of light the use of coloured filters would have to be used. The filters will be put in front of the lamp and made sure that no any other colour will be absorbed by the plant from the light, as this would affect the experiment and give the wrong results. The coloured light will then be directed to the pondweed using the same apparatus as used in the first experiment using the white light. This test will also be done three times to find a good average. This experiment will be done to see what affect different coloured light will have on a plant and the rate of photosynthesis by measuring the oxygen given by the plant. Results Table Colour of How much oxygen was given off per minute in arbitrary units Light Test 1 Test 2 Test 3 Average White 0.8 0.5 0.6 0.63 Red ...read more.


My results in my table did not follow my prediction as it is in the wrong way around. But the colour green was correct as it releases the least amount of oxygen. The reason why this could have happened is because of the surrounding lights around the plant that could have changed the amount of oxygen released. I could have changed and improved the experiment by making sure that the only light going in was the colour that I chose. Another way of improving my results is by making sure that the oxygen collected is from in the leaf and not from outside the leaf as this might not be from the reaction to produce oxygen. Although my results where inaccurate to my prediction I still think that they were good as they were consistent and there was only one anomalous result that still looked quite consistent. But I would not rely on these results because they are not correct. Such as the colours blue, yellow and orange. I could do more experiments for this investigation, as there are two more parameters that can be varied to change the release of oxygen in the plant. The two other factors are amount of carbon dioxide added and water added. I could also vary the amount of sunlight on the plant to change the amount of oxygen released. As a conclusion to this experiment I think my results were good enough to say that it fit my prediction and that with a little bit more precautions I could have proved my prediction completely correct. ...read more.

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