Question 9
Investigating how light intensity affects the rate of photosynthesis
Like the previous experiment, this experiment uses a water plant. You are going to change the amount of light that falls onto the plant and see how this affects the number of bubbles it produces in one minute.
You will need: a test tube containing water, a piece of water plant, a lamp, a beaker in which you can stand the test tube, a ruler for measuring the distance between the lamp and the test tube, a timer.
Safety: It is very important to keep electrical wires, plugs and the lamp away from the water.
Method
1 Set up your equipment. Place the lamp close to the test tube. Leave the equipment like that for about 5 minutes, to give the plant time to settle down and start to photosynthesise. While you are waiting, read the rest of these instructions and then draw a results chart. When you can see bubbles coming from the cut end of the plant stem, you can start your experiment.
2 Measure the distance between the lamp and the test tube, and write it down in your results chart.
3 Start the timer. Count how many bubbles the plant produces in one minute, and write this down.
4 Repeat step 3 two more times.
5 Now move the lamp a little bit further away from the test tube. Measure the new distance.
6 Repeats steps 3 and 4.
7 Repeat steps 5 and 6 for at least two more distances of the lamp, further from the test tube.
Like the previous experiment, this experiment uses a water plant. You are going to change the amount of light that falls onto the plant and see how this affects the number of bubbles it produces in one minute.
You will need: a test tube containing water, a piece of water plant, a lamp, a beaker in which you can stand the test tube, a ruler for measuring the distance between the lamp and the test tube, a timer.
Safety: It is very important to keep electrical wires, plugs and the lamp away from the water.
Method
1 Set up your equipment. Place the lamp close to the test tube. Leave the equipment like that for about 5 minutes, to give the plant time to settle down and start to photosynthesise. While you are waiting, read the rest of these instructions and then draw a results chart. When you can see bubbles coming from the cut end of the plant stem, you can start your experiment.
2 Measure the distance between the lamp and the test tube, and write it down in your results chart.
3 Start the timer. Count how many bubbles the plant produces in one minute, and write this down.
4 Repeat step 3 two more times.
5 Now move the lamp a little bit further away from the test tube. Measure the new distance.
6 Repeats steps 3 and 4.
7 Repeat steps 5 and 6 for at least two more distances of the lamp, further from the test tube.
