How to measure the maximum kinetic energy of electrons emitted due to photoelectric effect? From Einstein's photoelectric equation, $$hf = \phi + k.e_{\text{max}}$$ where $\phi$ is the work function of the metal.

My question is : how to experimentally determine the kinetic energy of electrons?

 A: From the formula hv =hv0 + KEmax .
Experimentally when electrons were on a stage of leaving the plate to move to positive terminal if u apply stopping potential the value of stopping potential will give the kinetic energy of electron
A: You can adjust the potential difference between the two metal plates in the setup of the photoelectric effect experiment.
Gradually decrease the potential difference from positive values to negative values until there is no current flowing through the circuit, i.e. when the reading of the galvanometer is zero. The potential difference when there is no current flowing through the circuit is known as the stopping voltage $V_s$.
The reason why there is no current when the p.d. is $V_s$ is that all the KE of an electron is converted to the electric potential energy that is equal to $eV_s$. Thus, even the most powerful electron is not able to reach the metal plate on the opposite side because its KE is not able to overcome the electric potential energy due to p.d. $V_s$.
