RPA 6: Investigate how light intensity affects photosynthesis

Question 1

What is the independent variable?

Answer 1

Distance of the light source from the pond weed

Question 2

What is the dependent variable?

Answer 2

number of bubbles produced in 1 minute or volume of gas in the gas syringe

Question 3

What are the control variable?

Answer 3

• Volume of sodium hydrogen carbonate
• species of pond week
• time counting bubbles for

Question 4

Why might an LED bulb be better?

Answer 4

LED doesn’t heat up the solution

Question 5

Why is sodium hydrogen carbonate used?

Answer 5

to supply the pondweed with carbon dioxide

Question 6

How could you improve the investigation?

Answer 6

• use volume instead of number of bubbles
• video the bubbles to double check counting
• use a heatproof screen
• LED bulb

Question 7

Describe and explain the trend that the graph will shows

Answer 7

As the light gets further from the pondweed, the number of bubbles produced decreases because there is less light for photosynthesis

Question 8

What is the inverse square law?

Answer 8

As the distance of the light increases, the light intensity decreases - this means if you double the distance the intensity will quarter.

Question 9

What is the inverse square law equation?

Answer 9

light intensity=1/distance^2 (squared)