By referring to the photoelectric effect, state what threshold frequency means.
Light of a particular wavelength falls on a metal surface and electrons are emitted. Explain why those emitted electrons have a spread of kinetic energies below a maximum value.
The incident radiation has wavelength $\lambda$. Figure 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 using the work function energy.
Use your answer to part (i) to calculate the work function energy $\phi$.
Caesium metal has a work function energy of $2.2 \times 10^{-19}\,\text{J}$. On the axes in Fig. 7.1, sketch the graph that shows how $E_{\text{MAX}}$ varies with $1/\lambda$ for caesium metal.