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How Does Light intensity affect the rate of Photosynthesis?

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How Does Light intensity affect the rate of Photosynthesis? Introduction All green plants need to be able to make their own food. They do this by a process called photosynthesis. For this to occur they need sunlight energy. This energy is absorbed by a green pigment called chlorophyll, which is mainly found in the leaves. This energy then combines with water molecules from the soil and carbon dioxide from the air. Then, as a result of this, a type of sugar is produced .This is called glucose. Oxygen is also made. For my experiment I have chosen to use light distance as my variable. This means that to carry out a fair test everything else must be kept the same during the experiment. Prediction I think that as the light source is moved closer to the pond weed, the more bubbles will be produced. This is because the light will be more intense and therefore increase the rate of photosynthesis as the intenser the light; the faster the rate of photosynthesis. ...read more.


Diagram Method * Collect apparatus. * Set up apparatus as in diagram shown. * Fill beaker with water. * Set up lamp in correct position (e.g. 100cm). * Turn on lamp and start stopwatch. * Count the bubbles for the next two minutes and also make a note of the change in volume. * Record your results. * Repeat experiment twice more for distance 100cm and then do the same with distances 75cm, 50cm, 25cm and finally 0cm (or as close to). Results Distance (Cm) 1st attempt (Bubbles) 2nd attempt (Bubbles) 3rd attempt (Bubbles) Average (Bubbles) 100cm 6 8 4 6 75cm 14 20 15 16 50cm 24 26 23 24 25cm 45 49 47 47 0cm 56 64 62 62 Graph Conclusion Looking at my results a can see a significant increase in the rate of photosynthesis as the distance decreases. All of the results show this pattern. In the experiment when the distance was 100cm there was not much photosynthesis taking place only about 6 bubbles of oxygen were produced. ...read more.


I believe my measurements were about as accurate as I could get using the apparatus that I did. I experienced a few problems with the experiment. One problem I encountered was the change in temperature when the lamp was too close to the pondweed. I could not do anything accept to put the Perspex in front of the lamp and this did not do much. In an ideal experiment I would use a sodium bulb which is the equivalent to natural sunlight and does not create any heat. This would have created even better results. Another problem we faced was counting the bubbles when the plant was photosynthesising. The bubbles were different sizes, therefore making impossible to count every bubble and getting perfect results. Although the bubbles were not counted 100% accurately I still managed to get very good results and am very pleased with the information I have found. To take this investigation further I could investigate the amount of bubbles produced by seaweed in salt water under a lamp at different distances. This would make interesting comparison with the pondweed and I would get some good overall results. ?? ?? ?? ?? 1 ...read more.

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