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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 Green plants don't exude food from the soil they make their own, using sunlight. This is called photosynthesis, which means "making through light". This occurs in the cells of a green plant, which are exposed to sunlight. Four things are needed to make this process work and this gives two thing: the four things needed are light from the sun, carbon dioxide diffuses from the air, water from the soil and chlorophyll in the leaves. This gives out oxygen which is released into the atmosphere and glucose which is used for biomass and energy. The word equation for the process of photosynthesis is: Carbon Dioxide + water Glucose + oxygen The energy which is produced is used to build up smaller molecules into larger molecules. Here are some uses of energy: * Sugars into starch * Sugars into cellulose- needed for cell walls * Sugars, nitrates and other nutrients for protein- for growth and to make to enzymes * Sugars into lipids for storing in seeds Factors affecting photosynthesis Temperature, carbon dioxide concentration and light intensity can interact to limit the rate of photosynthesis. Any one of them, at a particular time, maybe the limiting factor. Carbon Dioxide can have an effect on the plant because plants need carbon dioxide to photosynthesize. ...read more.


I will vary the distance because this will show us that the further the lamp is the rate of photosynthesis will decrease. This does not mean that if I move the lamp away from 5 cm to 10 cm that the light intensity will be half. I will keep the weed the same because if we use different weeds then it will not be a fair test because some plants are better and quicker then others. We will keep the water the same because then the temperature can differ and also we will have to keep on adding sodium bicarbonate and we can't always get the exact amount. What I expect to happen is explained in the hypothesis. We will be able to do a trial experiment 1st which will show us that the experiment is set up and it is working. We will do the experiment twice which will help us work out averages and also if there are anomalous results we will find out what went wrong and redo that bit of the experiment again. What we need to do in order to get the experiment working. 1) Set up the apparatus as shown in the diagram 2) When the weed has settled down and is producing bubbles then start the clock and time it for 1 minute and see how many bubbles have came up. ...read more.


If I did the experiment again I would measure the temperature because an artificial light which was the lamp gives out 12 joules per second of light energy and 48 joules per second heat energy because it was a filament bulb. If we used a low energy bulb then it would have gave 12 joules per second light energy and 3 joules per second heat energy. Because we used a filament bulb we had more heat then light and so the temperature can be a limiting factor in some cases. To make it a fair test we could have used a low-energy bulb which is more efficient and less heat is given out but they are too expensive. I had enough results to reach a conclusion and my results prove that light intensity is effects the rate of photosynthesis: the further the light the slower the rate of photosynthesis. The change I suggested could have made the results more reliable because if a filament bulb which we were using gives out 4 times as much heat then light then the limiting factor can be the temperature. If we use the low energy bulb then that give 4 times less heat and more light which we need. If we do the investigation again I would use a low-energy bulb to get more accurate and reliable results. I have carried out a fair trial. Davinder Singh Poonia 10/1 ...read more.

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