February/March 2026 Paper 12

In the $\alpha$-particle scattering experiment, a beam of $\alpha$-particles is aimed at a thin gold foil. Most of the $\alpha$-particles go straight through or are deflected by a small angle. A very small proportion are deflected by more than $90^{\circ }$, effectively rebounding towards the source of the $\alpha$-particles. Which conclusion about the structure of atoms cannot be drawn from this experiment alone?