By reference to the photoelectric effect, state what is meant by the threshold frequency.
Electrons are emitted from a metal surface when light of a particular wavelength is incident on the surface. Explain why the emitted electrons have a range of values of kinetic energy below a maximum value.
The wavelength of the incident radiation is 
. The variation with 
of the maximum kinetic energy 
of electrons emitted from a metal surface is shown in the figure below.
Use the figure above to determine, without reference to the work function energy, the threshold frequency 
.
Use your answer in (i) to calculate the work function energy 
.
Caesium metal has a work function energy of 
. On the axes of the figure above, sketch a graph to show the variation with of for caesium metal.
.
.
