Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: Explain that the CMBR was produced shortly after the Universe was formed and that this radiation has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded
Learning Objective/s:
  • Describe the conditions of the early Universe that led to recombination.
  • Explain how photon decoupling created the Cosmic Microwave Background Radiation.
  • Analyse how cosmic expansion red‑shifts the CMBR into the microwave region.
  • Interpret the CMBR’s temperature and isotropy as evidence for the Big Bang model.
Materials Needed:
  • Projector and slide deck
  • Whiteboard and markers
  • Printed worksheet with timeline and spectrum data
  • Short video clip of CMBR detection (e.g., COBE/Planck)
  • Interactive simulation (online or app) of wavelength stretching
  • Exit‑ticket cards or clicker system
 Introduction:

Show a striking microwave‑sky map and ask students what they think it represents. Review that they already know the basic Big Bang timeline and the electromagnetic spectrum. State that by the end of the lesson they will be able to explain how the CMBR originated and why it is now observed in the microwave region.
Lesson Structure:
  1. Do‑now (5 min): Quick quiz on the Big Bang timeline and key epochs.
  2. Mini‑lecture (10 min): Present recombination, photon decoupling, and the birth of the CMBR using slides.
  3. Interactive simulation (10 min): Students adjust the cosmic scale factor to see how photon wavelengths stretch from visible/infrared to microwave.
  4. Group worksheet activity (10 min): Analyse CMBR spectrum data and answer guided questions.
  5. Class discussion (5 min): Connect CMBR isotropy and temperature to evidence for a hot, dense origin.
  6. Exit ticket (5 min): Write one sentence summarising how expansion shifts the CMBR into the microwave region.
Conclusion:

Recap the chain from the hot early Universe, through recombination, to the stretched microwave photons we detect today. Collect exit tickets to check understanding, and assign a short reading on CMBR anisotropies with a prompt to formulate one question for the next class.