Question

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?
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 20%
a there is nothing wrong with the experiment.
b he should add a control group with a co₂ level of zero ppm and a light intensity of zero percent
c he should only grow one plant in each group
d he should only change the wavelength of light for each group.

Explanation:

In a scientific experiment to determine the effect of a single variable (light wavelength in this case), all other variables (like \(CO_2\) level and light intensity) should be kept constant. Here, \(CO_2\) level and light intensity vary across groups along with light wavelength. This violates the principle of controlling variables.

Answer:

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