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Unit 4: Wave Models and Quantum Physics
Quick questions on Radioactivity and half-life: WACE Year 12 Physics Unit 4
3short 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 are the three decay modes?Show answer
Alpha decay emits an alpha particle, a helium-4 nucleus (), reducing the mass number by and the atomic number by . Beta-minus decay emits an electron when a neutron becomes a proton, raising the atomic number by with the mass number unchanged. Gamma decay emits a high-energy photon as an excited nucleus settles to a lower energy state, changing neither the mass number nor the atomic number. Alpha is the least penetrating and gamma the most.
What are balancing nuclear equations?Show answer
In any nuclear equation the total mass number (top) and the total atomic number (bottom) must be the same on both sides. For example, alpha decay of radium-226:
What are calculating with half-lives?Show answer
After whole half-lives, the fraction remaining is
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