10- different wavelengths of light and photosynthesis

What are the types of pigments found in chloroplasts?

Primary pigment and accessory pigments.

What is the purpose of having different accessory pigments?

To absorb a wider range of wavelengths of light.

Why is sodium hydrogen carbonate added?

To supply carbon dioxide for photosynthesis.

What does the volume of gas produced indicate?

It is assumed to be oxygen, so the volume of gas is proportional to the rate of photosynthesis.

What are the controlled variables of this practical?

• Light intensity (distance from lamp)

• Amount of sodium hydrogen carbonate

• Time allowed for gas collection

• Temperature

How is the light intensity controlled?

By using different coloured filters to cover one side of the beaker close to the lamp, and covering the other side using tin foil.

Outline the procedure to this practical.

1. Place a piece of pondweed in a beaker of water.

2. Cover one side of the beaker with the tin foil, and cover the other side of the beaker with one of the light filters.

3. Add half a spatula of sodium hydrogen carbonate to the water to provide carbon dioxide. Leave for 5 minutes.

4. Place the bench lamp a set distance from the beaker.

5. Set up the photosynthometer. Leave for 5 minutes.

6. Record the volume of gas produced during this time.

7. Replace the filter with another colour of filter and repeat the experiment.