| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Define the half-life of a particular isotope as the time taken for half the nuclei of that isotope in any sample to decay; recall and use this definition in simple calculations, which might involve information in tables or decay curves (calculations |
Learning Objective/s:
- Define half‑life and explain why it is a constant for a given isotope.
- Apply the half‑life formula to calculate remaining nuclei or mass from tables or decay curves.
- Interpret decay curves to determine the number of half‑lives elapsed and the half‑life itself.
- Identify and avoid common pitfalls such as unit mismatches and misreading the definition.
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Materials Needed:
- Projector or interactive whiteboard
- Printed worksheet with isotope tables and decay‑curve sketches
- Scientific calculators (or calculator app)
- Isotope data cards (e.g., ¹⁴C, ¹³¹I, ²³⁸U)
- Whiteboard and markers
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Introduction:
Begin with a quick poll: “What everyday items rely on radioactive decay?” Connect responses to the concept of half‑life. Review the previous lesson on nuclear stability. State that by the end of class students will be able to calculate and interpret half‑life problems accurately.
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Lesson Structure:
- Do‑Now (5'): Students answer a short question on half‑life definition on the board.
- Mini‑lecture (10'): Present the definition, formula, and key points using slides.
- Guided practice (12'): Work through the provided worked example (I‑131 decay) together, highlighting each step.
- Interactive activity (15'): In pairs, students use isotope data cards to solve a table‑based problem and sketch a decay curve.
- Check for understanding (5'): Quick quiz via clicker or show of hands on common pitfalls.
- Wrap‑up (3'): Summarise main ideas and answer lingering questions.
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Conclusion:
Recap the half‑life definition and the step‑by‑step calculation method. Ask students to write one exit‑ticket answer: “What is the most common mistake when using half‑life equations?” Assign homework to complete three additional problems from the worksheet, including one decay‑curve interpretation.
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