Physics 9702 · AS & A Level · Atoms, nuclei and radiation
Atoms, nuclei and radiation — practice question
A radioactive source that emits $\alpha$-particles is positioned beneath the plates. As shown in Fig. 7.1, the arrangement consists of two parallel vertical metal plates in a vacuum, joined to a power supply and a switch. The route of the $\alpha$-particles is already shown on Fig. 7.1. When the switch is closed, a potential difference (p.d.) appears across the plates, creating a uniform electric field in the gap. The plate spacing is $12\ \text{mm}$.
(a(i))[1]
On Fig. 7.1, sketch the route of the $\alpha$-particles.
(a(ii))[1]
Explain why the metal plates are placed in a vacuum.
(a(iii))[2]
Calculate the p.d. needed to create an electric field of $140\ \text{MV m}^{-1}$.
(b)[3]
The $\alpha$-particle source is swapped for a $\beta$-particle source. Using the properties of $\alpha$-radiation and $\beta$-radiation, suggest three ways in which the deflection seen with $\beta$-particles could differ.
(c)[1]
Complete Fig. 7.2 to show how the proton number $Z$ and the nucleon number $A$ of different radioactive nuclei change when an $\alpha$-particle or a $\beta$-particle is emitted.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “curved track towards the negative ($-$) plate on the right-hand side” …