| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: infer from the results of the α-particle scattering experiment the existence and small size of the nucleus |
Learning Objective/s:
- Describe the historical context and limitations of the Thomson “plum‑pudding” model.
- Explain how the Rutherford α‑particle scattering experiment demonstrates the existence of a tiny, dense nucleus.
- Calculate an estimate of nuclear radius using the back‑scattering energy relation.
- Apply the empirical formula R = r₀A^{1/3} to compare nuclear and atomic sizes.
- Evaluate the significance of the experiment for the development of the modern nuclear model.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint slides with diagram of the scattering apparatus
- Handout summarising observations and key formulas
- Calculator or spreadsheet for radius‑estimation activity
- Video or animation of the gold‑foil experiment
- Whiteboard and markers
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Introduction:
Begin with a striking question: “What would happen if a tiny particle smashed into an atom?” Connect this to students’ prior knowledge of the Thomson model and state that by the end of the lesson they will be able to explain how Rutherford’s experiment revealed a hidden nucleus and estimate its size.
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Lesson Structure:
- Do‑now (5') – Quick write‑up on the strengths and weaknesses of the Thomson model.
- Mini‑lecture (10') – Historical background and why the Thomson model was challenged.
- Demonstration (15') – Show diagram/video of the Rutherford apparatus; discuss key observations.
- Guided calculation (15') – In pairs, use the energy‑conservation formula to estimate the nuclear radius for gold.
- Concept discussion (10') – Compare the estimated radius with atomic size; introduce the empirical R = r₀A^{1/3} relationship.
- Check for understanding (5') – Exit ticket: one sentence explaining why large‑angle scattering proves a concentrated nucleus.
- Summary (5') – Teacher recaps objectives and links to next topic on nuclear stability.
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Conclusion:
Re‑emphasise that the scattering experiment provided direct evidence of a tiny, massive nucleus occupying only a minute fraction of the atom. Collect exit tickets, then assign a brief homework task: use the empirical formula to calculate the radius of a carbon‑12 nucleus and compare it with the Rutherford estimate.
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