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LearnCambridge97022025–2027Paper 1 · Multiple ChoiceParticle physics

Paper 1 · Module

Particle physics

2 subtopics≈ 70 min in total

Start the module: Atoms, nuclei and radiation Open graphing calculator

Atoms, nuclei and radiation
The α-scattering experiment showed that an atom's mass and positive charge are concentrated in a tiny nucleus. A nuclide is written $^A_Z\text{X}$ ( $A$ nucleons, $Z$ protons). Unstable nuclei emit α (a helium nucleus), β⁻ (an electron plus an antineutrino), β⁺ (a positron plus a neutrino) or γ (a photon). Nucleon number and charge are conserved in every decay.
≈ 35 min
Fundamental particles
Protons and neutrons are made of quarks. There are six flavours: up ( $+\tfrac23e$ ), down ( $-\tfrac13e$ ), strange ( $-\tfrac13e$ ), charm ( $+\tfrac23e$ ), top ( $+\tfrac23e$ ) and bottom ( $-\tfrac13e$ ), each with an antiquark of opposite charge. Hadrons are baryons (three quarks) or mesons (quark + antiquark). Leptons, such as electrons and neutrinos, are fundamental. In β⁻ decay a down quark becomes an up quark; in β⁺, up becomes down.
≈ 35 min