Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: Describe experiments to distinguish between good and bad absorbers of infrared radiation
Learning Objective/s:
  • Describe how experimental setups can differentiate good and bad infrared absorbers.
  • Explain the relationship between absorptivity, emissivity and temperature change in the experiments.
  • Analyse temperature data to identify which material is a good absorber.
  • Evaluate safety procedures when handling infrared sources and hot plates.
Materials Needed:
  • Two identical metal plates (one matte black, one matte white)
  • Infrared lamp with constant power supply
  • Thermometers or thermocouples
  • Insulating stand and clamps
  • Timer or stopwatch
  • IR detector or thermopile with voltmeter
  • Samples: black cardboard, aluminium foil, clear glass, plastic film
  • Protective goggles and heat‑resistant gloves
 Introduction:
Begin with a quick demonstration of a heated lamp warming a black surface faster than a white one to spark curiosity.
Review prior knowledge of infrared radiation and the concept of absorptivity versus emissivity.
Explain that by the end of the lesson students will be able to design and interpret experiments that identify good and bad IR absorbers.
Lesson Structure:
  1. Do‑Now (5') – students answer a short question on why some surfaces feel hotter under sunlight.
  2. Mini‑lecture (10') – recap IR radiation, Stefan‑Boltzmann law, and absorptivity.
  3. Demonstration (10') – teacher shows black vs white plate heating; students note observations.
  4. Guided lab activity (20') – students set up the black‑body/white‑body experiment and record temperatures.
  5. Data analysis (10') – groups plot temperature vs time, compare rates, and draw conclusions.
  6. Extension & safety check (5') – brief discussion of the transmission experiment and review safety checklist.
Conclusion:
Summarise how temperature trends reveal good versus bad absorbers and link this to emissivity values.
Ask each student to write one sentence on the safety precautions needed when working with IR lamps as an exit ticket.
For homework, assign a short report designing an experiment to measure the emissivity of an unfamiliar material.