Lesson 2: Ocean Wave Physics: Swell Intersections, Refraction & Interference
Exploring physical phenomena—waves, forces, vectors, optics, and relativity—through traditional Polynesian navigation and ocean science.
🎯 Ngā Whāinga Akoranga | Learning Intentions
Wave physics parameters (wavelength , frequency , wave speed , period ), ocean swell generation, wave refraction around islands, and constructive/destructive interference.
Calculate wave speed and frequency, model ocean swell patterns with a ripple tank or simulation, and identify island wave diffraction signatures.
🎥 Media Anchor & Pedagogical Scaffold
How do Ocean Waves Work? — Concerning Reality
Video (4 min, Concerning Reality): An animated explainer on how waves are generated, how they travel through water, and the physics behind swell patterns and interference.
🧠 1. Before Viewing (Activate & Predict)
How can navigators feel island interference patterns in ocean swells through the motion of a waka hull?
👁️ 2. During Viewing (Watch With a Job)
Watch the full 4-minute clip and record the evidence for each key mechanism:
- Wave generation: What creates waves in the ocean, and what factors affect their size?
- Wave propagation: How do waves move through water, and what is the relationship between wavelength, frequency, and wave speed?
- Constructive and destructive interference: What happens when two waves meet?
🗣️ 3. After Viewing & Kaiako Move (Process & Apply)
Kaiako Move: Demonstrate a ripple tank generating two-point interference patterns and island barrier diffraction.
Immediate Task: Complete Section 2 of your Navigation Physics Logbook: Wave Interference & Refraction Calculations.
⚡ Whakaoho | Do Now: A Wave Does Not Carry the Water Anywhere
Float something small in a container of still water and tap one end. Two minutes: watch the floating object as the wave passes it.
Does it travel along with the wave, or does it bob and stay put? Whatever crosses an ocean, it is not the water itself. Write down what you think is actually moving.
📖 Activity 1: Measure the Wave, Then Bend It Around an Island
Measure and calculate (13 min). In the ripple tank or simulation, measure wavelength and count frequency, then calculate v = f λ. Do it at two different frequencies and check whether v stays the same. At a fixed water depth it should — if your two answers differ a lot, find the measurement that slipped.
Put an island in the way (12 min). Place an obstacle in the tank. Sketch how the wavefronts bend around it and where two wave trains cross. That crossing pattern is the actual signal: a navigator reading swell interference can detect an island well before it is visible.
📝 Activity 2: Navigation Physics Logbook & Problem Solving (20 mins)
Portfolio Section 2. Submit: (1) two wave-speed calculations from measured wavelength and frequency, with units; (2) a labelled sketch of refraction around your obstacle; (3) an explanation of how two crossing swells can indicate land beyond the horizon — and what conditions would make that signal hard or impossible to read.
🏫 Kaiako Planning & Pedagogy Notes
Year 10 Curriculum Alignment: NZ Curriculum Science Phase 4 — Physical World & Earth/Space Systems. Integrates traditional Polynesian wayfinding (Mātauranga Waka) with foundational NCEA Level 1 Physics mechanics, wave behaviour, and optics.