Lesson Plan

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Lesson Plan
Grade: Date: 18/01/2026
Subject: Physics
Lesson Topic: Know that ionising nuclear radiation can be measured using a detector connected to a counter
Learning Objective/s:
  • Describe how ionising radiation is detected and converted into electrical pulses.
  • Explain the relationship between count rate, detection efficiency and source activity.
  • Compare different detector types and select the appropriate one for a given radiation.
  • Calculate detection efficiency from a given count rate and activity.
  • Apply safety procedures when handling radioactive sources and detectors.
Materials Needed:
  • Geiger‑Müller tube or other radiation detector
  • Electronic counter/display
  • Low‑activity sealed radioactive source
  • High‑voltage power supply and pulse amplifier
  • Lead, aluminium and paper shielding
  • Safety goggles and lab coat
  • Worksheet with sample questions
  • Projector and screen for diagrams
 Introduction:
Begin with a striking fact: a single particle from a distant star can be detected on Earth using a simple detector. Review students' prior knowledge of ionising radiation types (α, β, γ) and how they interact with matter. Explain that by the end of the lesson they will be able to describe detector operation, calculate detection efficiency, and apply safety measures.
Lesson Structure:
  1. Do‑now (5') – quick quiz on radiation types and hazards.
  2. Mini‑lecture (10') – principle of detection and overview of detector types, using projector.
  3. Demonstration (10') – connect a GM tube to a counter, show real‑time counts from a source, discuss signal amplification.
  4. Guided practice (12') – students work through the sample efficiency calculation in pairs, using worksheet.
  5. Group discussion (8') – compare detectors, discuss suitability and safety; teacher checks understanding with concept questions.
  6. Exit ticket (5') – each student writes one key point about detector‑counter connection and one safety rule.
Conclusion:
Summarise that detectors convert ionising events into pulses which are tallied by a counter to give a count rate linked to activity via efficiency. Ask students to submit an exit ticket stating the formula R = ε A and one safety precaution. For homework, assign a short problem set calculating efficiencies for different detector scenarios.