biology - how light intensity affects the rate of photosynthesis

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Biology Coursework ¡V Does The Light Intensity
Affect the Rate of Photosynthesis

The Investigation

In this experiment I will investigate the affect in which the light intensity will have on a plants photosynthesis process. This will be done by measuring the bubbles of oxygen and having a bulb for the light intensity variable.


The input variable which will be used in this investigation will be the light intensity (this will be a 100Watt bulb being moved closer and further away from the plant). The outcome variable which will change as a result of this experiment will be the amount of oxygen made in the experiment due to the amount of light intensity increases (causing the plant to photosynthesise more).


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The reason in which I will keep the other variables the same is because if increased they would increase the rate of photosynthesis making the experiment pointless and a waste of time. Also if they decrease then it will be likely that the rate of photosynthesis will decrease as well. Me and my partner in this experiment decided that we will set the timer to start after sixty seconds in which the light has been turned on, we chose this because the photosynthesis rate will have been rising and be at a steady rate to take the amount of bubble recording after one minute. We will be doing each light intensity test three times to get an average (for our graphs).


The apparatus I will be using are:
Clamp Stands
Test Tube
100Watt Bulb and Light
Plastic Screen
Automatic Counter
1 Metre Ruler
Light Meter

Preliminary experiment

The preliminary experiment was done to find out what range of values I will use and details of the measuring instruments. I decided that the amount of water will fill the test tube, the light intensity readings will be at 100cm, 75cm, 50cm and 25cm on the metre ruler, the stop watch will be turned on after 60 seconds of the light been on and the results will be taken three times and put into a results table. The results my partner and I ended up with where:
100Cm between light and plant = 6 bubbles
25Cm between light and plant = 12 bubbles
I will be measuring the light intensity with a light meter at
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