A scientist wants to determine the best light wavelength for growing plants. He grows plants in four test groups as shown in the table below. What, if anything, was wrong with the experiment.

Question

Group Light Wavelength CO2 Level Light Intensity
A (10 Plants) 400 nm 400 ppm 30%
B (10 Plants) 500 nm 700 ppm 80%
C (10 Plants) 600 nm 600 ppm 50%
D (10 Plants) 700 nm 200 ppm 80%

A. He should only grow one type of plant in each group.
B. He should only change the wavelength of light for each group.\
C. He should add a control group with a level of zero ppm and a light intensity of zero percent.
D. There is nothing wrong with the experiment.

Answer 1

The primary issue with the experiment is that multiple factors (light wavelength, CO2 level, and light intensity) are varied simultaneously across the different test groups. This makes it difficult to determine the specific effect of light wavelength on plant growth since any observed differences in growth could be attributed to changes in CO2 levels or light intensity instead.

Therefore, the correct answer is:

B. He should only change the wavelength of light for each group.

This would help isolate the effect of light wavelength by keeping CO2 levels and light intensity constant across all groups, allowing for a more accurate assessment of the best light wavelength for plant growth.