| Lesson Plan |
| Grade: |
Date: 01/12/2025 |
| Subject: Physics |
| Lesson Topic: recall and use I = I0e–μx for the attenuation of ultrasound in matter |
Learning Objective/s:
- Recall the exponential attenuation law I = I₀e⁻ᵐᵘˣ and define each variable.
- Explain how the attenuation coefficient μ depends on frequency and material properties.
- Apply the attenuation equation to calculate intensity, distance or μ in quantitative problems.
- Interpret how attenuation influences ultrasound resolution and penetration depth.
- Compare different ultrasound transducer types and relate their operation to attenuation effects.
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Materials Needed:
- Projector and screen
- Printed worksheet with example calculations
- Scientific calculators (or calculator app)
- Handout of a piezoelectric transducer diagram
- Laptop with an ultrasound attenuation simulation (e.g., PhET)
- Clickers or online response system for quick checks
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Introduction:
Begin with a short video clip of a fetal ultrasound scan to capture interest. Ask students what physical factors might affect the image quality, linking to prior knowledge of wave frequency and intensity. State that by the end of the lesson they will be able to use the attenuation formula I = I₀e⁻ᵐᵘˣ to solve real‑world problems and explain its relevance to medical and industrial applications.
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Lesson Structure:
- Do‑now (5 min): Quick quiz on wave frequency, wavelength and intensity concepts.
- Mini‑lecture (10 min): Derive and discuss I = I₀e⁻ᵐᵘˣ, define μ, and show its frequency dependence with a diagram.
- Guided example (12 min): Work through the sample calculation (μ = 0.5 m⁻¹, x = 0.03 m) in pairs; teacher circulates to check understanding.
- Interactive simulation (8 min): Students vary μ and f on the laptop simulation and observe intensity decay.
- Application discussion (10 min): Small groups evaluate how attenuation limits medical imaging versus industrial NDT, then share key points.
- Formative check (5 min): Exit ticket – solve a new problem using the attenuation equation.
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Conclusion:
Summarise the relationship between frequency, attenuation, and image quality, confirming that students can now manipulate the exponential law. Collect the exit tickets and remind learners to complete the worksheet homework, which includes three varied attenuation problems to reinforce the day's learning.
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