Nuclear Physics: Key Terms (Form 5 SPM Physics)

Terms and definitions

• Nucleus, The small, dense, positively charged centre of an atom, made up of protons and neutrons.
• Isotope, Atoms of the same element that have the same number of protons but different numbers of neutrons.
• Radioactivity, The spontaneous emission of radiation (alpha, beta or gamma) from the unstable nuclei of certain atoms.
• Alpha particle, A particle made of two protons and two neutrons (a helium nucleus) emitted by some radioactive nuclei; it has a positive charge and low penetrating power.
• Beta particle, A high-speed electron emitted from the nucleus when a neutron changes into a proton; it has a negative charge and moderate penetrating power.
• Gamma ray, A high-frequency electromagnetic wave emitted by an unstable nucleus; it has no charge and very high penetrating power.
• Radioactive decay, The random process by which an unstable nucleus loses energy by emitting radiation and changes into a more stable nucleus.
• Half-life, The time taken for half the radioactive nuclei in a sample to decay.
• Nuclear fission, The splitting of a heavy nucleus into two lighter nuclei, releasing a large amount of energy.
• Nuclear fusion, The joining of two light nuclei to form a heavier nucleus, releasing a large amount of energy, as happens in the Sun.
• Nuclear energy, The energy released from changes in the nucleus of an atom, such as fission or fusion, described by E = mc².
• Mass defect, The difference between the total mass of the separate nucleons and the mass of the nucleus they form, which is released as energy.
• Free body diagram, A diagram that shows all the forces acting on a single object, drawn as arrows from the object. (related term from another chapter)
• Inclined plane, A flat surface set at an angle to the horizontal, on which an object's weight can be resolved into components along and perpendicular to the surface. (related term from another chapter)
• Elasticity, The property of a material that allows it to return to its original shape and size after the force deforming it is removed. (related term from another chapter)

Content standards these terms come from

• 6.1 Radioactive Decay
• 6.2 Nuclear Energy

How to learn them

1. Cover the definition, say it aloud, then check the unit.
2. Pair each term with a formula or experiment from the chapter.
3. Write the Malay term alongside the English one, SPM papers are bilingual.

More Nuclear Physics resources

• Chapter overview: Nuclear Physics
• Revision Notes
• Common Mistakes
• Practice Questions
• Paper 2 Answering Guide
• Paper 3 Guide
• Calculation practice sets

Source: DSKP KSSM Physics Form 4 and 5 (Versi English), Sijil Pelajaran Malaysia: Format Pentaksiran mulai 2021, Fizik (4531) (Bahagian Pembangunan Kurikulum (BPK), KPM)