AQA · A level Physics

Superallowed alpha decay A-level Physics challenge

Can you get 100%? Use the rapid decay of tellurium-104 to test nuclear equations, half-life, tunnelling and experimental evidence.

Read about the first superallowed alpha decay

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Question

8 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

Tellurium-104 has proton number 52 and emits an alpha particle. Write the balanced nuclear equation and identify the daughter nucleus.

[2 marks]

1(b)

A sample initially contains 8000 tellurium-104 nuclei. Its half-life is 18 ns. Calculate the expected number of undecayed tellurium-104 nuclei after 54 ns.

[2 marks]

1(c)

The alpha particle is bound inside the nucleus by the strong interaction but faces an electrostatic potential-energy barrier as it leaves. Explain how quantum tunnelling allows alpha decay and why an unusually high tunnelling probability gives a very short half-life.

[2 marks]

1(d)

The decay occurs so quickly that the daughter tin-100 is identified from a following decay in the same detector. State two experimental checks that would strengthen the claim that the two signals form one decay chain.

[2 marks]

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