By using the photoelectric effect, state what the term threshold frequency means.
Light of a certain wavelength is incident on a metal surface, causing electrons to be emitted. Explain why the emitted electrons have a spread of kinetic energies below one maximum value.
The incident radiation has wavelength $\lambda$. Fig. 7.1 shows how the maximum kinetic energy $E_{\text{MAX}}$ of electrons emitted from a metal surface varies with $1/\lambda$.
Use Fig. 7.1 to determine the threshold frequency $f_0$ without referring to the work function energy.
Use your answer in (i) to find the work function energy $\Phi$.
Caesium metal has a work function energy of $2.2 \times 10^{-19}\,\text{J}$. On the axes of Fig. 7.1, draw a graph to show how $E_{\text{MAX}}$ varies with $1/\lambda$ for caesium metal.