Physics 9702 · AS & A Level · Atoms, nuclei and radiation
Atoms, nuclei and radiation — practice question
A feature of $\alpha$-particles is that, at atmospheric pressure, they cause air to become highly ionised. During this ionisation process, a neutral atom changes into an ion pair. That ion pair consists of a positively charged particle and an electron.
(a(i))[1]
State the meaning of an $\alpha$-particle.
(a(ii))[1]
State an approximate distance range for $\alpha$-particles in air at atmospheric pressure.
(b(i))[1]
Show that $8.5 \times 10^{-13}\,\text{J}$ is equivalent to $5.3\,\text{MeV}$.
(b(ii))[2]
Calculate, to two significant figures, how many ion pairs are created as the $\alpha$-particle is brought to rest in air at atmospheric pressure.
(b(iii))[2]
Using your answer in (a)(ii), estimate the average number of ion pairs produced per unit length of the $\alpha$-particle track as it is brought to rest in air.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “helium nucleus or a particle containing two protons and two neutrons” …