Photoelectric Effect problem 26

Work function energy is the minimum amount of energy required for an electron to escape from the surface of a metal.

The emitted electrons have a range of kinetic energy up to a maximum value because electrons are arranged at different levels in a metal. The electrons below the surface of the metal would use a part of the energy of the photon to first move to the surface of the metal, and the remaining part of the energy becomes their kinetic energy. However, the electrons already at the surface would not need to use a part of the photon energy to move to the surface of the metal; they have the maximum energy.

Therefore, even when the incident light is monochromatic, the emitted electrons have a range of kinetic energy up to a maximum value.

The work function energy of the metal surface is .

Intensity determines the number of photons arriving at the metal surface per unit time, and this determines the number of electrons emitted per unit time. Therefore, the graphs in (i) and (ii) do not depend on the intensity of the incident radiation because intensity only determines the number of electrons emitted per unit time and not the maximum energy for the metal.