A non mono chromatic light is used in an experiment on photo electric effect. The stopping potential is related to the

For photo electronic effect is observed, wavelength of the incident light (λ) should be less than the threshold wavelength (λ₀​) of the metal.

Einstein's photoelectric equation,
${\mathrm{eV}}_0 = \frac{\mathrm{hc}}{\mathrm{\lambda }} - \mathrm{\varphi }$

It is clear from the above equation that stopping potential is related to the shortest wavelength.