| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: show an understanding of experiments that demonstrate two-source interference using water waves in a ripple tank, sound, light and microwaves |
Learning Objective/s:
- Describe the conditions for constructive and destructive interference for water, sound, light, and microwaves.
- Explain how fringe spacing relates to wavelength, source separation, and screen distance.
- Apply the formula Δy = λD/d to calculate wavelength from experimental data.
- Conduct a ripple‑tank demonstration and interpret the observed nodal and antinodal lines.
- Compare interference patterns across four different wave media.
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Materials Needed:
- Ripple tank with two dippers and strobe light
- Two identical speakers, microphone and sound level meter
- Monochromatic laser, double‑slit slide and screen
- Microwave transmitter, double‑slit plate and movable detector
- Rulers, calculators and data sheets
- Projector and PowerPoint slides for theory
- Safety goggles for laser work
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Introduction:
Imagine hearing a whisper become louder in one spot and softer in another simply by moving a microphone. Students already understand basic wave properties and the principle of superposition, which we will extend to interference. By the end of the lesson they will be able to predict and measure interference patterns in water, sound, light and microwaves.
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Lesson Structure:
- Do‑now (5 min): Quick quiz on wave superposition and phase relationships.
- Mini‑lecture (10 min): Review coherent sources, path difference, and the Δy = λD/d relation.
- Ripple‑tank demonstration (12 min): Set up, observe fringe pattern, measure Δy and calculate λ.
- Sound interference activity (12 min): Position speakers, move microphone along rail, record intensity maxima/minima, determine λ.
- Light & microwave stations (15 min): Small groups rotate between laser double‑slit and microwave set‑up, collect data and compute wavelengths.
- Guided analysis (10 min): Compare results across media, discuss sources of error, and answer concept‑check questions.
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Conclusion:
We recap how each experiment confirms the same interference principles and how the measured fringe spacings lead to wavelength calculations. For the exit ticket, students write one similarity and one difference between two of the media studied. Homework: complete a worksheet applying Δy = λD/d to a new set of data for a chosen wave type.
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