The Effects of Light Intensity and Wavelength on the
Rate of Photosynthesis
Overview of Reaction
In this simulation, you will be manipulating two variables: light intensity and light wavelength. The amount
of ATP produced will change depending upon the set parameters. Go to "Johnson Explorations:
Photosynthesis" located at http://www.mhhe.com/biosci/genbio/biolink/j_explorations/ch09expl.htm . Look
over the diagram before clicking on "skip intro" so you have a fair idea what is going on, the above
diagram will also help.
Procedure: Your task is to use the simulation to determine how wavelength and intensity affect the rate of
photosynthesis (and the production of ATP). Keep in mind you are dealing with two variables, so in order
to determine absolutely how each factor affects photosynthesis, you must keep one variable constant
while manipulating the other variable.
Lab Report must contain the following typed sections.
1. Introduction: Describe briefly the light dependent reactions and propose a hypothesis to answer the
experimental question.
2. Data: Include data tables for the simulation. The tables must show clearly trends resulting from
changes of intensity and changes of wavelength. Multiple data tables would probably be best here. In
Microsoft Word, use the "table" function to organize your data.
3. A graph showing how the percentage of ATP changed (Y axis) as a result of changes in wavelength
and intensity (X axis). Two graphs would be best here. You may use Create A Graph to make your
graphs, or use a spreadsheet or graphing program of your choice.
4. Conclusion: Use your data to answer the experimental question. Answer clearly how light wavelength
affects the reaction, and how light intensity affects the reactions. Offer an explanation of the results,
taking into account the principles of photosynthesis and the light reaction.