(a)[1]
State the meaning of work function energy.
(b)[2]
The way the maximum kinetic energy $E_{K}$ of photoelectrons emitted from the surface of sodium metal varies with frequency $f$ is shown in Fig. 7.1. Use the gradient of Fig. 7.1 to determine a value for the Planck constant $h$. Show your working.
(c)[3]
The sodium metal in (b) has a work function energy of $2.4\,\text{eV}$. It is replaced with calcium, whose work function energy is $2.9\,\text{eV}$. On Fig. 7.1, draw a line to show how the maximum kinetic energy $E_{K}$ of photoelectrons emitted from the surface of calcium varies with frequency $f$.