Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Biology
Lesson Topic: interpret absorption spectra of chloroplast pigments and action spectra for photosynthesis
Learning Objective/s:
  • Describe the characteristic absorption spectra of chlorophyll a, chlorophyll b, and carotenoids.
  • Explain how an action spectrum reflects pigment absorption and quantum efficiency.
  • Analyse provided spectra to identify pigment contributions and evaluate any mismatches.
  • Predict how changes in light quality influence the overall photosynthetic rate.
  • Apply the equation R(λ)= Σ φᵢ Aᵢ(λ) I(λ) to interpret experimental data.
Materials Needed:
  • Projector and screen
  • Printed handouts of absorption and action spectra
  • Spectrophotometer data sheets (sample data)
  • Coloured LED light sources (blue, red, green)
  • Worksheets with analysis checklist
  • Whiteboard and markers
 Introduction:
Plants appear green because chlorophyll absorbs poorly in the middle of the visible spectrum. Review of basic photosynthesis concepts will be quickly checked, and students will be told they must be able to link pigment absorption peaks to photosynthetic efficiency by the end of the lesson.
Lesson Structure:
  1. Do‑now (5'): Quick question on why leaves are green – students write a short answer (checks prior knowledge).
  2. Mini‑lecture (10'): Present absorption spectra of chlorophyll a, chlorophyll b, and carotenoids using the projector.
  3. Guided analysis (12'): In pairs, students overlay pigment λmax on the action spectrum handout and complete the provided checklist.
  4. Whole‑class discussion (8'): Groups share observations; teacher highlights coincidences and mismatches, linking them to quantum yield and energy loss.
  5. Application activity (10'): Using the equation R(λ)= Σ φᵢ Aᵢ(λ) I(λ), students calculate the expected photosynthetic rate at 660 nm and compare with the given data.
  6. Exit ticket (5'): Each student writes one key insight about the relationship between absorption and action spectra.
Conclusion:
We recap how pigment absorption peaks shape the action spectrum and why deviations indicate physiological regulation. The exit ticket responses are collected for immediate feedback, and for homework students will read the textbook section on light‑quality effects and draft a brief plan for selecting LED lights for optimal plant growth.