Lesson Plan

Resources → Subject Notes → Physics → Notes
Lesson Plan
Grade: Date: 18/01/2026
Subject: Physics
Lesson Topic: Describe how wavelength and gap size affects diffraction through a gap
Learning Objective/s:
  • Describe how wavelength and gap size influence the diffraction angle.
  • Explain the relationship θ ≈ λ⁄a and predict the strength of diffraction.
  • Apply the concept to real‑world examples such as light, radio and water waves.
  • Compare diffraction outcomes for different a : λ ratios.
  • Use the qualitative summary table to justify exam‑style answers.
Materials Needed:
  • Projector with slides showing formula and summary table
  • Whiteboard and markers
  • Laser pointer or LED with adjustable slit apparatus
  • Ruler or measuring tape for gap measurements
  • Worksheet with practice questions
  • Exit‑ticket cards
 Introduction:
Begin with a short video of water waves spreading after passing through a narrow opening to capture interest. Ask students to recall how they have seen light bend around corners, linking to prior knowledge of wave behavior. Explain that by the end of the lesson they will be able to predict diffraction patterns using the λ⁄a relationship.
Lesson Structure:
  1. Do‑now (5'): Quick worksheet question on everyday diffraction examples (check).
  2. Mini‑lecture (10'): Define diffraction, derive θ ≈ λ⁄a with diagram.
  3. Demonstration (10'): Laser through adjustable slit; students record how changing gap size affects spread.
  4. Guided analysis (10'): Compare observations with the formula; fill in a table of a vs λ scenarios.
  5. Group activity (10'): Each group selects a real‑world case (radio, water, light) and predicts diffraction strength; present findings.
  6. Formative quiz (5'): Kahoot/MCQ to confirm understanding before moving on.
Conclusion:
Recap that larger wavelengths or smaller gaps produce wider diffraction angles, reinforcing the θ ≈ λ⁄a rule. Have each student write an exit‑ticket stating which factor dominates in a given scenario. For homework, ask students to research a technology that relies on diffraction and prepare a brief description.