Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: understand that an antiparticle has the same mass but opposite charge to the corresponding particle, and that a positron is the antiparticle of an electron
Learning Objective/s:
  • Describe the relationship between mass and charge for particle–antiparticle pairs.
  • Explain why antiparticles have opposite electric charge and quantum numbers.
  • Identify the positron as the electron’s antiparticle and list its properties.
  • Calculate the energy of photons produced in electron‑positron annihilation using E=mc².
Materials Needed:
  • Projector or interactive whiteboard
  • Slide deck on antiparticles and positrons
  • Handout with particle‑antiparticle table
  • Cloud‑chamber video or animation
  • Worksheet with calculation problems
  • Clickers or polling tool for quick checks
 Introduction:
Begin with a short video of cloud‑chamber tracks showing opposite curvature for electrons and positrons to spark curiosity. Review students’ prior knowledge of electric charge and rest mass from previous lessons. State that by the end of the lesson they will be able to describe antiparticle properties and predict the outcome of electron‑positron annihilation.
Lesson Structure:
  1. Do‑now (5’) – Quick quiz on charge sign and mass of electrons (using clickers).
  2. Direct instruction (10’) – Present key properties of antiparticles and the positron, using slides and the particle‑antiparticle table.
  3. Demonstration (8’) – Show cloud‑chamber video and explain Anderson’s discovery; discuss charge reversal.
  4. Guided practice (12’) – Students work in pairs on worksheet calculations of annihilation photon energies, teacher circulates for feedback.
  5. Check for understanding (5’) – Exit poll: students write one sentence summarizing why the positron has opposite charge but same mass.
Conclusion:
Summarise that antiparticles share mass with their partners but carry opposite charge, and that positron‑electron annihilation produces two 511 keV photons. Ask students to complete an exit ticket describing one real‑world application of positrons. Assign homework to read a short article on PET imaging and solve two additional annihilation problems.