One way to proof the validity of \(f_{osc}\) and the associated \(I_{osc}=q_e*f_{osc}\) where \(q_e\) is the electron charge, is to pass such a current, \(I_{osc}\), through a metal whose photoelectric threshold frequency cannot be obtained (usually where the expected threshold frequency is at the edge of the producible light spectrum) during the experiment to obtain the threshold frequency.
In another words, repeat the experiment to obtain \(f_{threshold}\) with \(I_{osc}\) following through the metal.
To find where there was none...
