Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: recall and use intensity = power/area and intensity ∝ (amplitude )2 for a progressive wave
Learning Objective/s:
  • Describe the definition of wave intensity and its relation to power and area.
  • Explain why intensity is proportional to the square of the amplitude for a harmonic progressive wave.
  • Apply I = P/A⊥ and I ∝ A² to solve quantitative problems involving sound or light waves.
  • Identify common misconceptions about intensity and correct them.
Materials Needed:
  • Projector or interactive whiteboard
  • Slides with diagrams of progressive waves
  • Calculator or spreadsheet for calculations
  • Handout with example problem and summary table
  • Speakers or tone generator for a live demo
  • Rulers/measuring tape for area demonstration
 Introduction:
Begin with a short video clip showing a speaker and a laser pointer illustrating how changing volume affects brightness. Ask students to recall how power and area relate to intensity from previous lessons. State that today they will connect this idea to the amplitude‑intensity relationship and be able to predict intensity changes. Success will be measured by correctly solving a real‑world intensity problem.
Lesson Structure:
  1. Do‑now (5'): Quick quiz on definitions of power, area, and intensity.
  2. Mini‑lecture (10'): Derive I = P/A⊥ and discuss I ∝ A² using energy‑density concepts.
  3. Demonstration (8'): Use speaker and laser to show intensity change when amplitude (volume) is varied; students record observations.
  4. Guided practice (12'): Pairs work through the example problem on a worksheet.
  5. Concept check (5'): Exit‑ticket question – “If the amplitude is halved, how does intensity change?” Discuss answers.
  6. Misconception review (5'): Address common errors listed in the notes.
  7. Summary (5'): Recap key equations and take‑aways.
Conclusion:
Review the two core relationships I = P/A⊥ and I ∝ A², highlighting how they were used in the example. Students complete an exit ticket summarising one real‑world application. For homework, assign a set of intensity problems from the textbook, reminding them to ensure the area used is perpendicular to the direction of propagation.