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# How does the rate of photosynthesis alter with light intensity?

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Introduction

How does the rate of photosynthesis alter with light intensity? Results and Prediction Calculating light intensity (LI) I know that when the light was 10cm away from the plant, a light intensity reading of 1000 lux was obtained. I also know that as the distance increases, light intensity decreases. Therefore, light intensity is inversely proportional to the distance. However, as the distance doubles, light intensity is quartered. This means that light intensity is inversely proportional to the distance squared. So the relationship between light intensity and distance is "inverse squared". So this is how I will found out how to calculate light intensity: LI ??1 d2 1000 = 1 x constant 102 1000 = 1 x constant 100 1000 = 0.01 x constant 1000 = constant 0.01 100 000 = constant So LI = 1 x 100 000 d2 I also know that the rate of photosynthesis is directly proportional to the light intensity. ...read more.

Middle

This means that the amount of oxygen decreases, therefore the rate of photosynthesis decreases. This also means that distance is inversely proportional to the rate of photosynthesis. Graph 2 is related to graph 1 because instead of the distance of the light, light intensity is shown. The intensity of the light and the distance of the light are related because as the distance of the light from the plant decreases, the light intensity increases. Graph 2 goes through the origin which means that when there is no light, no photosynthesis happens. But as the light intensity increases, the average bubble length also increases proportionally. The straight line clearly shows this. However, in reality, the line levels off. This is because a further increase in light intensity doesn't result in a larger bubble length. This is because light intensity no longer becomes a limiting factor and the plant cannot produce more oxygen, instead other limiting factors come into play, such as temperature. ...read more.

Conclusion

Reading off a scale could cause me measuring it wrongly because I could not see the exact number with my eyes. The experiment could have been made fairer if I'd have used a piece of electronic equipment to measure the size of the bubbles. Another problem with the experiment could have been that the experiment was not reliable enough. There were many points of error in the experiment. For example, the lamp was not 100% efficient. It converted some of the energy to heat energy and this could have caused an increase in temperature inside the test tube. Heat gives more energy to the enzymes and this could have caused an increase in the rate of photosynthesis. Another problem was that I could not increase the light intensity with the same lamp. This was because the lamp was too near at 4000 lux for me to increase the intensity. This could have caused less accurate results. This could give an idea of another experiment I could do. I could do the exact same experiment, but instead use a brighter bulb. ?? ?? ?? ?? ...read more.

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# Related GCSE Green Plants as Organisms essays

1. ## Confirm which factors increases or decreases the rate of photosynthesis.

* No toxic chemicals to be handled directly. * Always do as instructed by a teacher * After each experiment benches must be tucked away. * Ethylated spirit is toxic and can cause blindness, therefore it is important to wear goggles.

2. ## How temperature affects the rate of photosynthesis.

Between these temperatures the light intensity stayed the same (at H) eliminating it from being a limiting factor and sodium hydrogen carbonate was provided in excess so that enough carbon dioxide was available for the reactions. The reactions involved in the light independent stage solely depend on temperature as their energy source.

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