Here’s the hypothesis for the duckweed experiemt

The controlled variables in an experiment are the ones that are kept the same for all trial runs, to ensure that no other factor except for the independent variable is being changed. In this case, the controlled variables are:

Timing of experiment: The timing of the experiment can be used as a controlled variable as a particular time constraint can be used to perform an experiment.

Duckweed population: The duckweed population should be kept as a constant to observe the impact of variables on the duckweed populations.

Environmental light: A particular environment light can be used as a standard under the influence of which the duckweed population shows growth.

Environmental temperature: A controlled standard temperature can be chosen for every trial to observe the growth of the duckweed.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach