For a given metal, there exists a certain minimum frequency of incident radiation below which no photoelectrons are emitted. This frequency is called the threshold frequency. Assuming given frequencies are above the threshold frequency, we see that increasing the frequency of the incident beam, keeping the number of incident photons or intensity fixed (this would result in a proportionate increase in energy) increases the maximum kinetic energy of the photoelectrons emitted because the photons impart more energy to the electrons, some of which is dissipated to break free while the rest comes out as kinetic energy. Thus more the frequency, hence more the photon energy and hence more the energy imparted to the electrons, thereby resulting in more maximum kinetic energy.