rate of photosynthesis

An Investigation to See
if Light Intensity Effects the
Rate of Photosynthisis.

I’m going to investigate the amount of light used in photosynthisis to see if it
has a noticable effect when you increase or decrease the light intensity.
Photosynthisis is the way in which light and carbon-dioxide is used by a plant to
produce energy in the form of starch.

6CO + 6H O = C H O + 6O

The factors that effect the rate of photosynthisis are the amount of light, the
amount of carbon-dioxide (CO ) and the temperature that can be used by the plant. I
have already carried out the experiment to see the effects on a plant when you
change the amount of carbon-dioxide. I found that the more carbon-dioxide used the
faster the plant photosynthisied. To see if this rule (More of a limiting factor = The
quiker the rate of photosynthisis) works, I will plan a experiment . My experiment
will be to see if the light intensity follows this rule. I will use a aquatic plant as they
can be used to see the effects under water.These plants still cotain chlorophyll (a
light absorbing die thats converts light energy intochemical energy).

To see if the amount of light intensity will effect the rate of photosynsis.

I predict that the more amount of light you allow the chlorophyll to absorb the
quicker the rate of photosynthisis will be. I think this because the amount of light is
a limiting factor in the reaction of photosynthisis. So if you alow more of a limiting
factor to be present in the chemical reaction it will all most certainly speed up the
rate of that reaction. If a plant had the right amount of carbon-dioxide and the right
temperature but the wrong amount of light the reaction of photosynthisis will be
slow. This is because the reaction needs the light to let the plant turn the light
energy to a chemical energy.

Fresh pond weed
250ml Beaker
Test Tube
Power Pack
200ml of Tap Water
1 Spactular of Sodium Bicarbonate
Stop Clock

Set up the Equipment
Add 200ml of Tap Water
Place the pond weed Inside the upside down Funnel
Add 1 Spactular of Sodium Bicarbonate Inside the Upside Down Funnel
Set the Lamp (thats connected to the power pack) to the Chosen distance Ethier
10,20,30,40,50cm away from the beaker
Start the Stop Clock and time for three Minutes
Count the Number Of Bubbles that the Pond Weed Gives off.
Remember Repeat This Experiment 6 Times Using a Different distance Each

Fair Test Points
Set the lamp to the same voltage
Take results for the same amount of time
Use the same amount of sodium bicarbonate


Distance of lamp Bubbles realised Average
from the plant in 3 minutes


A graph to show the effects of light to the rate of photosynthisis