Which independent variable should a student manipulate to test the hypothesis that green algae grow fastest when exposed to blue light?

To investigate the hypothesis that green algae grow fastest when exposed to blue light, it is essential to manipulate the variable that directly pertains to the growth condition being tested—in this case, the color of light. By varying the light color, the student can observe its effects on the growth rate of the algae. This means the student would set up different conditions where the algae are exposed to different colors of light, including blue, to see if it indeed promotes faster growth compared to other colors.

Manipulating the color of light allows the researcher to isolate the effect of light spectrum on algal photosynthesis and growth. Since photosynthesis is largely influenced by light wavelengths, testing different colors can yield valuable insights into how light influences the biological processes of the algae.