Design a practical experiment to investigate the effect of light wavelength on the rate of photosynthesis.

Aim: To investigate the effect of light wavelength/ colour of light on the rate of photosynthesis.

Materials: Glass Jar, test tube, cork, pond weed, clamp, small lamp, sticky tape, red, blue, yellow and green filters, Stopwatch, small knife.

Procedure:

Fill the glass jar nearly to the top with water.
Take one strand of pondweed and cut the end of the stem with a pair of scissors or razor.
Fill the test tube with water to the top of the cork. Slide the cut end of the pondweed stem through the hole in the cork so that they are held firmly in place.
Hold the test tube horizontally and then turn it upside down so that the pondweed enters the jar and attach the test tube to the clamp. Ensure that it is held firmly and that it is steady for safety reasons.
Take one of the coloured filters and wrap it around the jar. Use sticky tape to keep it in place if necessary.
Shine the lamp light onto the jar; make sure that it reaches the pondweed, at 10cm distance in each experiment so that the intensity of light will remain the same so that the results obtained are valid.
Leave the experiment for a minute or so that the plant adjusts to its surroundings and is photosynthesising at a regular pace.
After this, start the stopwatch and record the amount of bubbles evolved from the end of the plant in the test tube in 5 minutes.
Repeat this three times so that a fair average can be calculated.
Once the five minutes end, stop shining the lamp onto the pondweed and remove the coloured filter from around the jar.
Repeat the above processes, differing the colour of the filter wrapped around the jar each time, using either yellow, green, blue or red, using the same pond weed.

Pictures!?

Variables to be controlled in order to improve the validity of results obtained:

Distance that the light is shone- light intensity
Temperature- photosynthesis proceeds by a series of chemical reactions controlled by enzymes, which are sensitive to temperature. Around 30. Lower temp, rate slowed ???
Use the same piece of pond weed- otherwise the size of the pond weed may differ/ surface area may differ
Stopwatch
Repeat three times

Measurements

The way in which I will measure the rate of photosynthesis is by recording the amount of oxygen evolved from the plant that ...

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Sam Morran

15th of May 2013

This essay starts very well. It has a good method and some good results. It could be improved by adding some further explanation and writing a full conclusion. ***

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