Biology practical

Photosynthesis and light intensity

Move a lamp towards some pondweed, count the bubbles of oxygen each minute, and plot the rate against light intensity to find where it levels off.

What you will do

1. 01Put the lamp a distance d from the pondweed, with the heat shield in between.
2. 02Leave the pondweed for a minute to adjust to the new light.
3. 03Count the bubbles given off in one minute.
4. 04Repeat for at least five distances from about 10 cm to 80 cm.
5. 05Calculate light intensity as 1/d², plot the rate against it, and draw a smooth curve.