Answer: The excess energy is converted into kinetic energy for the motion of the ejected electrons.
Explanation: It requires a certain energy to eject an electron from a metal surface. This energy is known as the work function (W), which varies from metal to metal. Electrons can gain energy by interacting with photons. If a photon has an energy at least as big as the work function, the photon energy can be transferred to the electron and the electron will have enough energy to escape from the metal. A photon with an energy less than the work function will never be able to eject electrons.
So, a particular amount of energy is used to break the barrier and match the work function of the metal surface & the remaining energy is converted into kinetic energy for the motion of the ejected electrons.
