Hassan Mithani 9/11/17 Teacher: Miss. Williams Aims: The aim of the investigation was to find out how different light intensities affected the rate of photosynthesis within Elodea. Introduction and Hypothesis: Throughout our investigation we learned that light is the catalyst for the photosynthesis reaction. I believe that the rate of photosynthesis will increase according to the amount of light provided, until a certain point where the plant reaches its limit. Method We used several pieces of equipment. All we needed was a lamp, stopwatch, pondweed suspended in a water filled glass beaker and a meter stick. 1) Firstly, we placed our pondweed suspended in a water beaker, into a dark room on a raised platform for easy viewing. 2) After doing this, we placed our lamp over this at a distance of 20 centimeters. We used the stopwatch to time five minutes and switched the lamp on for a period of five minutes. Whilst this was happening, we counted the amount of bubbles that rose to the top due to photosynthesis. 3) After writing down our results on a table, we repeated this step 5 times, each time for a period of five minutes and each time bringing the lamp closer and closer by 5 cm to increase the light intensity. Each time we counted the amount of bubbles that rose and wrote the corresponding number into the table. 4) To complete our results and evaluation, we created a second results table to mimic the happenings of our experiment. As part of this we calculated the rate of photosynthesis by placing the amount of bubbles created through photosynthesis Risk Assessment In this experiment we will be interacting with hot apparatus such as lamps. These may harm our skin and as a precaution we should deal with utmost care towards these. There will also be a glass casing surrounding the pondweed. To protect ourselves from the glass, we should wear goggles to protect our eyes. We should also deal with the glass with utmost precaution. Variables Throughout the experiment, there were a number of variables we needed to know to organize the test and make it fair. The independent variable was the intensity of light, the dependent variable was the rate of photosynthesis which we measured by counting the bubbles. One control variable was the amount of elodea we used in each variation of the experiment. We controlled this by using the same untouched pot of Elodea for each variation. If we had not done this our results would have been unfair. Another control variable was the amount of time the elodea had to complete its photosynthesis. This was crucial for a fair experiment. Results Light Intensity Rate of Photosynthesis 5 cm 10 bubbles per minute 10 cm 5 bubbles per minute 15 cm 1 bubbles per minute 20 cm 2 bubbles per minute Our results show that the higher the light intensity, the faster the rate of photosynthesis. Therefore, my prediction was correct. However, there was a single anomaly in our data at 15 seconds. This went against the positive correlation of the rest of our results and hence we ignored it. Our results tell us that light intensity is a limiting factor of photosynthesis and that the more plants have, the higher their rate of photosynthesis would be. This is because light is a necessary factor which must be there to provide initial energy to kickstart the reaction. Therefore, the more light you introduce, the quicker the rate. Graph: Evaluation and Conclusion Throughout this experiment there were some aspects which could have been improved. If redoing the experiment, I would alter it as currently when we were moving the lamp forward to increase light intensity this also increased heat which may have caused the results we gained and ultimately created an unfair test. Within the experiment we also noticed a great deal of difference in results between groups. Next time we will be more selective about the similar type of elodea used. Due to the mentioned points, it is clear to us that this experiment may not have successfully completed its aim but rather gained an understanding of how heat and light intensity together effect the rate of photosynthesis.