# Bio Experiment Light Intensity

Topics: Light, Photosynthesis, Carbon dioxide Pages: 10 (2900 words) Published: June 12, 2011
Research question : How does the different light intensity affect the rate of photosynthesis in plants? Objective : To investigate the relationship between different light intensity (by having the source of light at different distance to the plant discs which is at; 10cm, 15cm, 20cm, 25cm, 30cm, and 35cm ) and rate of photosynthesis of plant. Introduction :

Photosynthesis is the process where light energy is absorbed by green plants to convert the raw materials (carbon dioxide and water) into sugars and oxygen (waste product). This conversion can be summarized into the equation below:

Raw materials Products

6CO2 + 6H2O C6H12O6 + 6O2 (light energy) waste product
Referring to the above equation, it can be seen that light energy plays the role as the source of energy stimulating the process of photosynthesis. The main pigment that absorbs light energy is chlorophyll which is the green pigment found inside chloroplasts. A green leaf cut out into discs of the same size are used in this experiment. This experiment is carried out to discover how different intensity would affect the rate of photosynthesis. Hypothesis : As light intensity increases, the rate of photosynthesis increases.

Variables :
Variables| Ways of controlling|
Independent variable :The distance of the source of light energy to the plant discs (light intensity).| Use different distance in each experiment by measuring using a 1 m ruler. The different distance are 10cm, 15cm, 20cm, 25cm, 30cm, and 35cm.| Dependent variable :Rate of photosynthesis | The rate of photosynthesis in each experiment is calculated by using the formula ;1tt = the time taken for each plant discs to float on the surface of 3% sodium hydrogen carbonate measured by using a stopwatch.| Controlled variable : * Number of plant discs used in each experiment * Concentration of sodium hydrogen carbonate solution * Volume of sodium hydrogen carbonate used * Size of plant discs * Source of light| Bu sing a cork borer, 5 discs measuring 8 mm in diameter each are cut out from the same leaf for each experiment. (Each experiment uses a set of 5 plant discs).Use the sodium hydrogen carbonate solution of 3% concentration only for each experiment.Use only 10ml of sodium hydrogen carbonate in each experiment measured by using a 20ml syringe.The plant discs are cut out by using the same cork borer with each of them having the diameter of 8mm each measured with 15cm ruler.The same desk lamp and its bulb is used in each experiment.| Table 1 : List of variables and ways to control them

Materials and apparatus :
Materials and Apparatus| Quantity| Volume/size|
Fresh green leaf| 1| 5 of 8mm discs for each experiment| 3% sodium hydrogen carbonate solution| 1 reagent bottle| 20ml for each experiment| Desk lamp| 1| -|
syringe| 6| 20 ml|
Stopwatch| 1| -|
1m ruler| 1| -|
15cm ruler| 1| -|
Cork borer| 1| -|
beaker| 66| 100ml50ml|
White tile| 1| -|
Measuring cylinder| 1| 100 ml|
Table 2 : list of materials and apparatus, their quantities, and volume or size used in the experiment. Methodology:
1. The distance between the bottom of the light bulb (from the desk lamp) and the surface of the laboratory table is adjusted at 10 cm. The lamp was turned on, and all other source of light was turned off. 2. 20 ml of 3% sodium hydrogen carbonate solution was measured by using a 100 ml measuring cylinder and then was poured into a 100 ml beaker. 3. 10 ml of the 3% sodium hydrogen carbonate solution was transferred into a 20ml syringe. 4. 5 of approximately 8mm in diameter...