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Unit 4: Wave Models and Quantum Physics

Quick questions on Atomic and nuclear physics: WACE Year 12 Physics Unit 4

4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is the Standard Model?
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The Standard Model groups fundamental particles into quarks and leptons. Protons and neutrons are not fundamental: each is made of three quarks (a proton is two up and one down, a neutron is one up and two down). Leptons include the electron and the neutrino. Forces are carried by exchange particles (for example the photon for the electromagnetic force).
What is mass-energy equivalence?
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Mass and energy are interchangeable,
What are nuclear reactions?
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In every nuclear reaction, nucleon number and charge are conserved. Radioactive decay includes alpha emission (a helium nucleus), beta emission (an electron from a neutron changing to a proton) and gamma emission (a high-energy photon as the nucleus de-excites). Fission splits a heavy nucleus into lighter fragments plus neutrons; fusion combines light nuclei. In each case the energy released equals the mass defect times c2c^2.
What is choosing the right energy relationship?
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Decide whether a question concerns the atom (use hf=EiEfhf=E_i-E_f with energy levels) or the nucleus (use E=Δmc2E=\Delta m\,c^2 with masses). Convert atomic mass units to kilograms and electronvolts to joules before substituting, and check that nucleon number and charge balance in any reaction equation.

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