Physics 9702 · AS & A Level · Radioactive decay

Radioactive decay — practice question

Polonium-193 $^{193}_{84}\text{Po}$ is an unstable nuclide. A nucleus of polonium-193 undergoes decay into a nucleus of lead-189 $^{189}_{82}\text{Pb}$ by emitting an alpha-particle.
(a(i))[1]

Radioactive decay is both random and spontaneous. State what is meant by random.

(a(ii))[1]

Radioactive decay is both random and spontaneous. State what is meant by spontaneous.

(b)[1]

Define half-life.

(c)[2]

Data for the binding energy per nucleon of the particles involved in the decay of a nucleus of polonium-193 are given. Determine the energy, in $\text{eV}$, released when a nucleus of polonium-193 decays into a nucleus of lead-189.

(d(i))[1]

A pure sample of polonium-193 contains $N_0$ nuclei. After a time $t$ the sample contains $N$ nuclei of polonium-193. The variation of $\ln\left(\frac{N}{N_0}\right)$ with $t$ is shown in Fig. 9.1. State the name of the quantity that is represented by the magnitude of the gradient of the line in Fig. 9.1.

(d(ii))[2]

Use Fig. 9.1 to determine the half-life, in ms, of polonium-193.

(e(i))[1]

Positron emission tomography (PET scanning) uses a radioactive tracer. State what happens to the positrons emitted by the tracer.

(e(ii))[1]

Explain why a tracer with a half-life of approximately 2 hours is a suitable tracer to use.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: It is impossible to predict when, or which nucleus, will decay

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