Question

The work function of a metal is 4.65ev and the metal is illuminated with a radiation of 6.86ev. what is the kinetic energy of the electron ejected from the surface of the metal

Answer 1

According to the Einstain's formula (see https://en.wikipedia.org/wiki/Photoelectric_effect#Theoretical_explanation), the kinetic energy is given as follows:

$$K = h\nu - W$$

where $h\nu = 6.86ev$ is the energy of radiation, $W = 4.65ev$ is the work function of the metal. Thus, obtain:

$$K = 6.86ev - 4.65ev = 2.21ev$$

Answer. 2.21ev.