Lesson Plan

• Describe the nature of sound as a longitudinal wave and its relation to frequency.
• Identify the frequency range that defines ultrasound (> 20 kHz).
• Explain why ultrasound is useful in medical imaging and industrial applications.
• Apply the formula v = f λ to calculate the wavelength of ultrasound waves.
• Compare ultrasound with audible sound and infrasound.

• Projector or interactive whiteboard
• Slide deck with frequency ranges and diagrams
• Handout containing the frequency table and v = f λ formula
• Audio clips demonstrating audible and ultrasound frequencies
• Short video showing an ultrasound scan
• Worksheet for practice calculations

Begin with a quick “guess the frequency” game using everyday sounds to hook interest. Review how frequency determines pitch and remind students of the audible range (20 Hz–20 kHz). State that today they will discover what lies beyond human hearing and how it is applied.

1. Do‑Now (5 '): Students list examples of sounds they hear daily and estimate their frequencies.
2. Mini‑lecture (10 '): Present the frequency spectrum, define ultrasound, and show the schematic diagram.
3. Demonstration (8 '): Play audio clips of audible vs. ultrasound (using a transducer) and discuss why we cannot hear the latter.
4. Guided practice (12 '): Work through the v = f λ formula with sample ultrasound frequencies; students calculate wavelengths.
5. Group activity (10 '): Analyze real‑world ultrasound applications (medical imaging, cleaning, sonar) and match them to benefits.
6. Check for understanding (5 '): Quick exit ticket – write one sentence defining ultrasound and one advantage.

Recap the definition of ultrasound and its key advantages, linking back to the earlier frequency examples. Collect exit tickets and assign a short homework: calculate the wavelength of a 30 kHz ultrasound wave in air and in water.