A monochromatic light beam illuminates a metal surface with work function \(\Phi\) in an evacuated phototube. An experimenter records the stopping potential \(V_s\) required to reduce the photocurrent to zero as a function of the light intensity for two different light sources: one with frequency \(f_1\) where \(hf_1 > \Phi\), and one with frequency \(f_2\) where \(hf_2 < \Phi\). Which of the following best describes the graphs of stopping potential \(V_s\) as a function of light intensity for each frequency?