State what is meant by the work function energy of a metal.
Ultraviolet radiation with frequency $1.36 \times 10^{15}\,\text{Hz}$ is incident, in a vacuum, on a metal surface. The power of the radiation arriving at the surface is $8.36\,\text{mW}$. Photoelectrons are emitted with a maximum kinetic energy of $3.09 \times 10^{-19}\,\text{J}$. Determine the number of photons incident on the surface per unit time.
Calculate the work function energy $\phi$ of the metal.
The frequency of the radiation incident on the surface in (b) is increased while the power remains constant. State and explain the effect of this change on the maximum kinetic energy of the photoelectrons.
The frequency of the radiation incident on the surface in (b) is increased while the power remains constant. State and explain the effect of this change on the rate of emission of photoelectrons.