Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: Know that all electromagnetic waves travel at the same high speed in a vacuum
Learning Objective/s:
  • Describe the nature of electromagnetic waves as transverse electric and magnetic fields.
  • Explain why all EM waves travel at the same speed c in a vacuum, referencing Maxwell’s constants.
  • Apply the relationship c = λ f to calculate frequency or wavelength for any region of the spectrum.
  • Distinguish the different regions of the EM spectrum based on wavelength/frequency, not speed.
  • Solve a sample problem converting the wavelength of visible light to its frequency.
Materials Needed:
  • Projector or interactive whiteboard
  • Slides with EM‑spectrum diagram
  • Worksheet with sample calculations
  • Calculators (or spreadsheet access)
  • Whiteboard and markers
  • Speed‑of‑light constant cards (optional)
 Introduction:
Begin with a quick demonstration: flash a laser pointer and ask students what determines how fast the light travels. Recall prior learning about wave propagation and the constant speed of light from earlier lessons. State that by the end of the lesson they will be able to explain why every type of electromagnetic radiation shares this speed and use c = λf for conversions.
Lesson Structure:
  1. Do‑now (5’) – short written question on wave speed versus medium; share answers.
  2. Mini‑lecture (10’) – present Maxwell’s derivation, introduce c = 1/√(ε₀μ₀) and show EM‑spectrum diagram.
  3. Guided practice (10’) – work through c = λf with examples from radio to gamma rays.
  4. Collaborative activity (10’) – groups calculate the frequency of a given wavelength (e.g., green light) using the worksheet.
  5. Concept check (5’) – quick quiz/Kahoot to confirm understanding that speed is constant.
  6. Summary discussion (5’) – recap key points and address any misconceptions.
Conclusion:
Summarise that all electromagnetic waves travel at 3.00 × 10⁸ m s⁻¹ regardless of wavelength or frequency. Ask students to write one sentence on an exit ticket describing how c = λf links wavelength and frequency. Assign homework: a set of conversion problems covering different regions of the spectrum.