Exam-style question
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In the beta‑decay of a neutron (n → p + e⁻ + β⁺), which of the following statements correctly describes the conservation of charge, baryon number and lepton number?.
- A.Charge is conserved, baryon number is conserved, lepton number is not conserved
- B.Charge is conserved, baryon number is not conserved, lepton number is conserved
- C.Charge is not conserved, baryon number is conserved, lepton number is conserved
- D.Charge is conserved, baryon number is conserved, lepton number is conserved
Model answer
What a good answer should say
- Charge is conserved, baryon number is conserved, lepton number is conserved.
- the correct option
Explanation
Why this works
The correct answer is Charge is conserved, baryon number is conserved, lepton number is conserved. It is the only option that matches the AQA A-Level Physics requirement for Applications of conservation laws; the distractors either apply to a different particle concept or reverse the relationship being tested.
Common mistake
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