Lesson Plan

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Lesson Plan
Grade: Date: 01/12/2025
Subject: Physics
Lesson Topic: explain photoelectric emission in terms of photon energy and work function energy
Learning Objective/s:
  • Describe the relationship between photon frequency, wavelength, and energy.
  • Explain how the work function determines the threshold frequency for photoelectric emission.
  • Calculate the maximum kinetic energy of emitted electrons using Kmax = hν – φ.
  • Predict the effect of changing light frequency and intensity on electron emission.
  • Apply these concepts to solve problems involving photon energy and work function.
Materials Needed:
  • Projector or interactive whiteboard
  • Slides with equations and diagrams
  • Worksheet with practice problems
  • Laser pointer or LED light source for demo
  • Metal plate sample (e.g., zinc) – optional
  • Calculator or simulation software (e.g., PhET Photoelectric Effect)
 Introduction:

Begin with a quick demonstration: shine a flashlight on a metal surface and ask students what they expect to happen. Recall prior learning about wave‑particle duality and energy quantisation. State that by the end of the lesson they will be able to explain how photon energy and the metal’s work function govern electron emission.
Lesson Structure:
  1. Do‑Now (5’) – Students answer a short question on photon energy (E = hν) on a sticky note.
  2. Mini‑lecture (10’) – Present equations for photon energy, momentum, and work function using slides and the summary table.
  3. Guided inquiry (12’) – In pairs, calculate kinetic energies for different metals given frequencies; teacher circulates.
  4. Demonstration (8’) – Show a laser hitting a metal plate; discuss why electrons are emitted only above a threshold frequency, not intensity.
  5. Concept check (5’) – Quick quiz (Kahoot) on threshold frequency and intensity effects.
  6. Application activity (10’) – Solve a real‑world problem (photoelectron spectroscopy) on the worksheet.
  7. Summary & reflection (5’) – Class discussion linking photon energy, work function, and observed results.
Conclusion:

Summarise that photon energy must exceed the work function for electrons to escape and that the excess appears as kinetic energy. Ask students to write a one‑sentence exit ticket stating the condition for photoelectric emission. Assign homework: complete additional problems calculating threshold wavelengths for various metals.