The student wanted to make the investigation of the effect of one-sided light more valid. The student decided to set up a third experiment. How should the student set up the third experiment?

A valid investigation needs proper controls to ensure the conclusion is correct. The original experiment compared one-sided light (Experiment 1) with no light (Experiment 2). To further confirm that the *direction* of the light is what causes bending, a third experiment with light from all sides (or directly overhead) should be set up. In this condition, the shoot should grow straight up, just like in the dark. This strengthens the conclusion that it is the uneven distribution of light that causes the bending.