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Science

Nuclear Physics

Overview

Students explore the nucleus of the atom, discovering how unstable nuclei decay, how half-life is used to measure radioactivity, and how enormous energy is released by nuclear reactions.

Learning Objective
Students understand the three types of radioactive decay, half-life, and the principles of nuclear fission and fusion.

Resources needed

  • None

Lesson stages

0 / 7 done
  1. 1 Recap atomic structure: the nucleus contains protons and neutrons. Some nuclei are unstable — they are radioactive.
  2. 2 Introduce alpha decay: a helium nucleus (2 protons, 2 neutrons) is emitted. The parent nucleus loses 2 protons and 2 neutrons.
  3. 3 Introduce beta decay: a neutron converts to a proton and an electron. The electron is emitted as a beta particle. Atomic number increases by 1.
  4. 4 Introduce gamma radiation: high-energy electromagnetic radiation emitted alongside alpha or beta decay. No change in nucleus composition.
  5. 5 Introduce half-life: the time taken for half the radioactive nuclei in a sample to decay. After each half-life, the count rate halves.
  6. 6 Introduce nuclear fission: a heavy nucleus (e.g. uranium-235) splits into two smaller nuclei when struck by a neutron, releasing enormous energy and more neutrons (chain reaction).
  7. 7 Introduce nuclear fusion: light nuclei (hydrogen isotopes) combine to form a heavier nucleus — the reaction that powers the Sun. Releases more energy per kilogram than fission.

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Variations

  • Calculate the remaining activity after several half-lives.
  • Draw a decay curve — activity vs time — and identify the half-life from the graph.
  • Discuss nuclear power: fission in controlled reactors vs fusion as a future energy source.
More information

Teach: radioactive, alpha, beta, gamma, half-life, fission, fusion, chain reaction, isotope. The key comparison: alpha is the heaviest and most ionising but least penetrating; gamma is the lightest and most penetrating.

Focus on the three decay types and their properties before introducing half-life. Introduce fission and fusion as applications after the decay concepts are secure.

Can students describe the three types of radioactive decay and state the penetrating power of each? Can they calculate the remaining activity after a given number of half-lives?

No resources needed. Draw decay schemes in soil. Graph half-life curves on any available surface. All calculations require only arithmetic.

Students often confuse nuclear fission with nuclear fusion. Fission splits heavy nuclei (used in nuclear power plants); fusion combines light nuclei (powers the Sun and is the focus of future energy research). They are opposite processes.

Nuclear physics underpins nuclear medicine, power generation, and our understanding of stellar energy. It also connects to particle physics — the frontier of fundamental science.