| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: understand that when a source of sound waves moves relative to a stationary observer, the observed frequency is different from the source frequency (understanding of the Doppler effect for a stationary source and a moving observer is not required) |
Learning Objective/s:
- Describe how motion of a sound source changes the observed frequency for a stationary observer.
- Derive and use the Doppler formula for a moving source.
- Calculate observed frequencies for approaching and receding sources using given data.
- Explain the relationship between wavelength, source speed, and frequency change.
- Apply the concept to real‑world examples such as sirens or train horns.
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Materials Needed:
- Projector or interactive whiteboard
- Slides with diagram of moving source and wavefronts
- Handout containing the Doppler formula and practice questions
- Calculator for each student
- Audio clips of siren sounds (optional)
- Whiteboard and markers
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Introduction:
Begin with a short video of an ambulance siren to capture interest, then ask students what they notice about pitch as the vehicle passes. Recall the relationship between speed, frequency, and wavelength from previous lessons. State that by the end of the lesson they will be able to predict and calculate the frequency heard when a source moves toward or away from a stationary observer.
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Lesson Structure:
- Do‑now (5') – Quick recall of wave basics (speed, frequency, wavelength); students write definitions on sticky notes.
- Mini‑lecture (10') – Introduce the moving‑source concept, display the compression/expansion diagram, and derive the Doppler formula on the board.
- Guided example (10') – Work through the ambulance calculation together, highlighting each substitution step.
- Pair activity (12') – Students solve the train‑horn problem from the handout, then compare answers with the teacher’s solution.
- Concept check (8') – Use clicker questions or show‑of‑hands to confirm understanding of frequency increase vs. decrease.
- Summary & reflection (5') – Recap key points, discuss everyday examples (e.g., passing cars), and collect exit tickets.
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Conclusion:
Review the main idea that a moving source changes the observed pitch while the speed of sound stays constant. Students complete an exit ticket stating one real‑world situation where the Doppler effect is important. Assign homework: complete the remaining practice questions and prepare a short explanation of how the effect would differ for a moving observer (for future study).
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