With reference to the photoelectric effect, state what is meant by work function energy.
The work function energy of a clean metal surface is 
. Electromagnetic radiation of wavelength 
is incident on the metal surface. The metal is in a vacuum
Calculate:
the photon energy
the maximum speed 
of the electrons emitted from the surface.
Explain why most of the emitted electrons will have a speed lower than .
The electromagnetic radiation incident on the metal surface may change in intensity or in frequency. Complete the table below by inserting either ‘increases’ or ‘decreases’ or ‘no change’ to describe the effects of the changes shown on the maximum speed and on the rate of emission of electrons.
.
.
