| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: describe and interpret qualitatively the evidence provided by electron diffraction for the wave nature of particles |
Learning Objective/s:
- Describe the de Broglie hypothesis and calculate the wavelength of an electron from its kinetic energy.
- Explain how the Davisson–Germer and LEED experiments demonstrate electron diffraction.
- Interpret diffraction patterns using Bragg’s law and differentiate wave‑ versus particle‑model predictions.
- Evaluate experimental evidence to justify the wave nature of electrons.
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Materials Needed:
- Projector with slide deck of diffraction diagrams
- Whiteboard and markers
- Printed handout summarising de Broglie formula and Bragg condition
- Simulation software (e.g., PhET) for electron diffraction
- Sample data sets from the Davisson–Germer experiment
- Worksheets for guided analysis
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Introduction:
Begin with a striking image of a diffraction pattern on a phosphor screen and ask students what they would expect if electrons were purely particles. Recall the de Broglie hypothesis and the concept of wavelength associated with moving matter, which they have previously derived. State that by the end of the lesson they will be able to explain how electron diffraction provides qualitative evidence for wave‑particle duality.
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Lesson Structure:
- Do‑now (5'): Quick quiz on de Broglie wavelength calculations.
- Mini‑lecture (10'): Review the de Broglie formula and introduce the Davisson–Germer apparatus with schematic slides.
- Demonstration (8'): Show a video/simulation of the Davisson–Germer experiment, highlighting intensity peaks at specific angles.
- Guided analysis (12'): In pairs, students use provided data to apply Bragg’s law, compare predicted and observed angles, and answer concept‑checking questions.
- Whole‑class discussion (5'): Summarise how discrete diffraction peaks support the wave model, contrast with particle expectations, and collect an exit‑ticket response.
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Conclusion:
Recap that electron diffraction patterns match the wavelengths predicted by de Broglie and satisfy Bragg’s law, confirming the wave nature of particles. Ask students to write one sentence on their exit ticket describing the key piece of evidence. For homework, assign a problem set requiring calculation of electron wavelengths for different accelerating voltages and prediction of diffraction angles.
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