Question 40 – Radioactivity - Edexcel IGCSE Physics Questions

In a variation of Rutherford's scattering experiment, researchers propose using helium-3 nuclei instead of standard alpha particles to probe a thin platinum foil.

A helium-3 nucleus is represented as $23He^{3}_{2}\text{He}$ .

State the number of protons and the number of neutrons in a helium-3 nucleus.

State the overall charge of a helium-3 nucleus in terms of the elementary charge $e$ .

The diagram below illustrates the experimental setup inside an evacuated chamber.

Rutherford-style scattering experiment setup with a collimated source, thin metal foil, and circular detector inside an evacuated chamber.

Explain why it is essential that the chamber is evacuated (i.e., a vacuum is maintained). Give two reasons.

Name and describe the force responsible for the deflection of the helium-3 nuclei.

Explain how the following two observations from the experiment led to specific conclusions about the structure of the atom:

Observation 1: The vast majority of the incident helium-3 nuclei passed straight through the platinum foil with virtually no deflection.
Observation 2: A very small fraction of the helium-3 nuclei were deflected by angles greater than $90∘90^\circ$ .