The effect of light on the rate of photosynthesis.

The bubbles are produced as a product of photosynthesis light energy is used to make food for the plant (glucose) and oxygen (the bubbles) is a product of this. The photosynthesis reaction is:

                Carbon dioxide+water       light          oxygen+glucose

                                                               chlorophyll            

The chlorophyll absorbs as much light as possible, so the closer the lamp the more light energy is absorbed the faster the rate of photosynthesis which also then produces more oxygen bubbles. Therefore the higher the results on the graph (number of oxygen bubbles) the faster plant are photosynthesis.

Evaluating

The method used was quite good for a simple experiment. But it doesn’t give a completely accurate result because the student may not be able to count all the oxygen bubbles produced. You could use an oxygen probe to measure the amount of oxygen more accurately. The anomalous results 5 bubbles in the first count when the lamp is 20cm away from the pondweed. And also 3 bubbles in the second count when the lamp is 25cm away from the pound weed. (Highlighted on the table)

These results may have occurred if the student miss counted or the equipment was set up incorrectly so as to let air in and oxygen bubbles where gained or lost. To prevent this two or more people could count or the equipment could be checked more thoroughly. These results are reasonable reliable as they come out as predicted the method is also tried and tested one which produces accurate3 results almost every time. Further work to extend the investigation could be repeating the test more times and also you could do the test using different coloured light filters to see the effect this has on photosynthesis.