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3.2 Particles and radiation

9 dot points across 9 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are particles classified into hadrons and leptons, and what conservation rules govern their interactions?

Hadrons (baryons and mesons), leptons, the conservation of baryon number, lepton number, strangeness and charge, the properties of the kaon and pion, and the decay of particles.
A focused answer to AQA A-Level Physics 3.2.1.5 and 3.2.1.6, covering hadrons (baryons and mesons), leptons, the conservation of baryon number, lepton number, strangeness and charge, and how these rules decide whether a particle interaction is allowed.
11 min answer →

What are the building blocks of the atom, and how do their charges and masses define each element and isotope?

Protons, neutrons and electrons, their relative charges and masses, proton number, nucleon number, isotopes and the use of the notation for representing nuclides, and specific charge.
A focused answer to AQA A-Level Physics 3.2.1.1, covering protons, neutrons and electrons with their relative charges and masses, proton and nucleon number, isotopes, nuclide notation, and how to calculate specific charge.
9 min answer →

How do discrete electron energy levels in an atom explain the emission and absorption of photons of specific wavelengths?

Discrete energy levels in atoms, excitation and de-excitation, ionisation, the relationship between photon energy and energy level difference, line spectra, and the operation of the fluorescent tube.
A focused answer to AQA A-Level Physics 3.2.2.2 and 3.2.2.3, covering discrete energy levels, excitation and ionisation, the photon energy equation linking level differences to wavelength, line spectra, and how the fluorescent tube works.
10 min answer →

How do the four fundamental forces act between particles through the exchange of virtual particles?

The four fundamental interactions, the concept of exchange particles (gauge bosons), the W bosons, the photon and the pion, and the use of Feynman diagrams to represent interactions such as beta decay and electron-proton collisions.
A focused answer to AQA A-Level Physics 3.2.1.4, covering the four fundamental forces, exchange (gauge) bosons, the W bosons and the photon, and how to draw and read Feynman diagrams for beta decay and electron-proton interactions.
10 min answer →

What is antimatter, and how are particles and photons created and destroyed in pair production and annihilation?

Antiparticles and their properties, the photon model of electromagnetic radiation, the photon energy equation, and the processes of annihilation and pair production with their energy calculations.
A focused answer to AQA A-Level Physics 3.2.1.3, covering antiparticles, the photon model, the photon energy equation, and the calculations behind annihilation and pair production using rest energies.
10 min answer →

Why does light release electrons from a metal only above a threshold frequency, and how does this prove light is made of photons?

The photoelectric effect, the threshold frequency and work function, the photoelectric equation, and how the effect provides evidence for the particle nature of electromagnetic radiation.
A focused answer to AQA A-Level Physics 3.2.2.1, covering the photoelectric effect, threshold frequency and work function, the photoelectric equation, and why the wave model fails while the photon model succeeds.
10 min answer →

What are quarks, and how do their combinations build the protons, neutrons and mesons we observe?

The properties of up, down and strange quarks and their antiquarks, the quark composition of baryons and mesons, the application of conservation laws to quark changes, and the quark model of beta decay.
A focused answer to AQA A-Level Physics 3.2.1.7, covering the charge, baryon number and strangeness of up, down and strange quarks, the quark composition of the proton, neutron, pions and kaons, and how beta decay is explained at the quark level.
10 min answer →

What holds a nucleus together, and why do some nuclei decay while others are stable?

The strong nuclear force and its range, the balance of forces in the nucleus, alpha, beta-minus and gamma radiation, and how the equation for beta-minus decay reveals the existence of the neutrino.
A focused answer to AQA A-Level Physics 3.2.1.2, covering the strong nuclear force and its range, why nuclei are stable or unstable, alpha, beta-minus and gamma radiation, and how the beta-minus decay equation gave evidence for the neutrino.
10 min answer →

How can light and electrons behave as both waves and particles, and what evidence supports each description?

The evidence for the wave nature of light and the particle nature of light, the de Broglie wavelength of a particle, electron diffraction as evidence for the wave nature of matter, and the link between momentum and wavelength.
A focused answer to AQA A-Level Physics 3.2.2.4, covering the evidence for the wave and particle natures of light, the de Broglie equation, electron diffraction as proof of the wave nature of matter, and how wavelength depends on momentum.
9 min answer →