| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: use IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient of a boundary between two media |
Learning Objective/s:
- Describe acoustic impedance and its relationship to density and sound speed.
- Apply the intensity reflection coefficient formula to calculate reflected intensity at a material boundary.
- Analyze how a matching layer reduces reflections and improves transmission.
- Evaluate typical impedance values for common media and predict echo strength.
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Materials Needed:
- Projector or interactive whiteboard
- Slide deck with diagrams and tables
- Worksheet with practice calculations
- Scientific calculators or online calculator tool
- Handout of typical acoustic impedance values
- Short video clip of ultrasound imaging (optional)
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Introduction:
Show a brief ultrasound video of a fetal scan and ask students what determines the brightness of the echo. Recall prior knowledge of wave speed, density, and impedance from earlier lessons. Explain that by the end of the class they will be able to calculate reflected intensity using the formula and describe the purpose of matching layers.
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Lesson Structure:
- Do‑now (5') – Quick quiz on definitions of acoustic impedance and wave speed.
- Mini‑lecture (10') – Review impedance, derive the intensity reflection coefficient \(I_R/I_0\) and work through the tissue‑bone example.
- Guided practice (15') – Pairs complete worksheet calculations using provided Z values; teacher circulates for support.
- Demonstration (5') – Play a video of ultrasound imaging; discuss how bright spots correspond to strong reflections.
- Matching‑layer activity (10') – Small groups design a matching layer using \(Z_m=\sqrt{Z_1Z_2}\) and calculate its quarter‑wavelength thickness.
- Check for understanding (5') – Exit ticket: compute \(I_R/I_0\) for a new media pair and justify the result.
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Conclusion:
Recap the definition of acoustic impedance, the reflection‑coefficient formula, and how matching layers improve transmission. Collect exit tickets, highlight common errors, and assign homework: additional calculation problems and a reading on industrial non‑destructive testing applications.
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