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3.8 Nuclear physics

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What are the properties of the three main types of ionising radiation, and how do we detect and shield against them?

The nature, penetration, ionising power and range of alpha, beta and gamma radiation, the inverse square law for gamma, background radiation and the uses and hazards of radiation.
A focused answer to AQA A-Level Physics 3.8.1.2 and 3.8.1.3, covering the nature, penetration, range and ionising power of alpha, beta and gamma radiation, background radiation, the inverse square law for gamma rays and the safe uses of radiation.
10 min answer →

How does the splitting of a uranium nucleus by a neutron lead to a self-sustaining chain reaction?

Induced nuclear fission by thermal neutrons, the chain reaction, critical mass, and the factors controlling whether the reaction is sustained.
A focused answer to AQA A-Level Physics 3.8.1.8, covering induced fission by thermal neutrons, the products of fission, the chain reaction, critical mass and the conditions needed to sustain a controlled chain reaction.
9 min answer →

Where does the enormous energy of nuclear reactions come from?

Mass and energy equivalence, mass defect and binding energy, the binding energy per nucleon curve, and the energy released in fission and fusion.
A focused answer to AQA A-Level Physics 3.8.1.7 and 3.8.1.8, covering mass and energy equivalence, mass defect, binding energy and binding energy per nucleon, the binding energy curve, and the energy released in nuclear fission and fusion.
10 min answer →

Why are some nuclei stable while others decay, and how can we predict the type of decay from a nucleus's composition?

The relationship between the numbers of neutrons and protons in stable and unstable nuclei, the N against Z graph, and predicting the mode of decay including alpha, beta-minus, beta-plus and gamma emission.
A focused answer to AQA A-Level Physics 3.8.1.5, covering the relationship between neutron and proton numbers in stable nuclei, the N against Z graph, and predicting alpha, beta-minus, beta-plus and gamma decay from a nucleus's position on the graph.
9 min answer →

How do we measure the size of a nucleus, and why is nuclear density the same for all atoms?

Estimating nuclear radius from closest approach of alpha particles and from electron diffraction, the dependence of radius on nucleon number, and the constancy of nuclear density.
A focused answer to AQA A-Level Physics 3.8.1.6, covering estimates of nuclear radius from alpha particle closest approach and electron diffraction, the relationship R proportional to the cube root of A, and the constant density of nuclear matter.
9 min answer →

How is the chain reaction in a nuclear reactor kept safe, controlled and useful?

The function of the moderator, control rods and coolant in a thermal nuclear reactor, the safety features, and the handling and disposal of radioactive waste.
A focused answer to AQA A-Level Physics 3.8.1.8, covering the roles of the moderator, control rods and coolant in a thermal nuclear reactor, the safety features that prevent uncontrolled reactions, and the handling and disposal of radioactive waste.
9 min answer →

If radioactive decay is random, how can we predict the behaviour of a large sample so reliably?

Radioactive decay as a random process, the decay constant, the activity of a source, the exponential decay law, half-life and applications such as radioactive dating.
A focused answer to AQA A-Level Physics 3.8.1.4, covering radioactive decay as a random process, the decay constant, activity, the exponential decay law, half-life and its link to the decay constant, and radioactive dating.
10 min answer →

How did the alpha scattering experiment reveal that the atom has a tiny, dense, positive nucleus?

The Rutherford alpha particle scattering experiment, the observations and conclusions, and how they led to the nuclear model of the atom.
A focused answer to AQA A-Level Physics 3.8.1.1, covering the Rutherford and Geiger and Marsden alpha scattering experiment, the key observations and the conclusions they support about the nuclear model of the atom.
9 min answer →