A metal sphere that is isolated and has radius $r$ is given charge so that the electric potential at its surface is $V_0$. On Fig. 5.1, sketch how electric potential varies with distance $x$ from the sphere's centre. Your graph must cover $x = 0$ to $x = 3r$.
Photons with wavelength $\lambda$ strike a metal surface. The greatest wavelength that still produces electron emission is $\lambda_0$. For photons of wavelength $\frac{\lambda_0}{2}$, the greatest kinetic energy of the emitted electrons is $E_{\text{MAX}}$. On Fig. 5.2, sketch the variation with wavelength $\lambda$ of the maximum kinetic energy for wavelengths from $\lambda = \frac{\lambda_0}{3}$ to $\lambda = \lambda_0$.
A pure sample of a radioactive isotope contains $N_0$ nuclei. The half-life of the isotope is $T_{\frac{1}{2}}$. The product of the radioactive decay is stable. Fig. 5.3 shows how the number $N$ of nuclei of the radioactive isotope varies with time $t$. On Fig. 5.3: mark on the time axis the points $t = 1.0T_{\frac{1}{2}}$ and $t = 2.0T_{\frac{1}{2}}$; sketch how the number of nuclei of the decay product varies with time $t$ from time $t = 0$ to time $t = T$.