Define threshold frequency, work function, and stopping potential w...

Question

Define threshold frequency, work function, and stopping potential with reference to photoelectric effect.

Accepted Answer

Threshold frequency ($f_0$): The minimum frequency of incident light below which photoelectric emission does NOT occur from a given metal surface, regardless of intensity.
$$\phi = hf_0$$
Work function ($\phi$): The minimum energy required to eject an electron from the surface of a metal.
$$\phi = hf_0 = \frac{hc}{\lambda_0}$$
SI unit: Joule (J) or electron volt (eV).
Stopping potential ($V_0$): The minimum negative potential applied to the anode in a photoelectric cell that just stops the most energetic photoelectrons from reaching the anode.
$$eV_0 = KE_{max} = hf - \phi$$
SI unit: Volt (V).