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Investigation: Photosynthesis & Light Intensity

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GCSE SCIENCE INVESTIGATION: PHOTOSYNTHESIS & LIGHT INTENSITY Aim: The aim of this experiment is to investigate how the intensity of light will affect the rate of photosynthesis in Kabambe (pondweed). To do this, Kabambe was placed in varying light intensities to test the amount of bubbles given off from a cut end to show the rate of photosynthesis occurring. Intro: 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 chemical equation for photosynthesis can be expressed as: (light) 6CO2 + 6H2O = C6H12O6 + 6O2 (in the presence of chlorophyll). Now from most experiments involving photosynthesis it has been seen that without light, the plant or organism will most certainly die. This is to rule out one null hypothesis that without light, no photosynthesis will take place. Light intensity affects the rate of photosynthesis because firstly a change in value would directly change the balancing factor of the equation, as stated above, therefore raising a output of the equation, e.g. most light would need more carbon dioxide and water to increase the amounts of glucose and oxygen, without there will be a limiting factor to the amount of light that can be put into the input part of the equation before photosynthesis cannot occur in an structured environment. ...read more.


the main experiment to show a correlation between the two, to state whether or not the size of the bubbles actually do cause a major difference, or if the size of the bubbles does not really matter that much overall. The results from the preliminary are as follows: DISTANCE FROM BEAKER (CM) LIGHT INTENSITY (1/D2) AMOUNT OF BUBBLES 40 1/160 = 0.00625 029 30 1/090 = 0.01000 039 20 1/040 = 0.02500 060 10 1/020 = 0.05000 080 00 1/100 = 1.00000 102 This is displayed in the graph as follows: Obtaining Evidence As decided in the preliminary experiment, the main experiment was only carried out twice; these have been added to the table below, and the average given. DISTANCE FROM BEAKER (CM) LIGHT INTENSITY 1ST REPEAT 2ND REPEAT AVERAGE 40 0.00625 032.0 030.0 031.0 30 0.01000 041.0 040.0 040.5 20 0.02500 060.0 059.0 059.5 10 0.05000 074.0 079.0 079.0 00 1.00000 096.0 105.0 101.5 A graph has also been produced to show the distance from beaker against the average amount of bubbles produced. A best fit curve has also been shown on it. O.4a O.6a O.8a O.4b O.6b Analysis: From the above table it is seen that firstly, the further the lamp is away from the beaker, the lower the light intensity (based on the equation "Light Intensity = 1/d2"). ...read more.


solution which may have meant that the repeats may have differed, but as it happens there was not much fluctuation in this, and the repeats are near exactly the same. These various inaccuracies show that although the experiment was sound, there are various methods in which the experiment can be carried out with more exact detail, providing more truthful data. However, due to limited time and equipment, the experiment was conducted in the best way possible given the situation. This was good enough to support my hypothesis, and to finalize a conclusion. Of course, the easiest way to produce more accurate results would be to take many repeats of the experiment, and in a longer time span, of which would give more time to correct the inaccuracies. Also, this experiment has been able to show the rate of photosynthesis against light of a full spectrum of colors. It would be interesting to investigate the rate of photosynthesis again varying colors, and to see if different colours contain varying amounts of energy. It would also be interesting to investigate the rate of photosynthesis when additional solvents are added to the water, and to see which solvents affect the rate of photosynthesis, this could also lead to investigating the optimum pH level for photosynthesis to take place. T.Durden 11W Biology - Science Investigation ...read more.

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