Lesson 2 of 8 · Waves
Particle Motion Decides the Wave Type
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🎯 Your mission
Predict it first. Then prove yourself right (or wrong).
⚡ The twist
Nature loves to surprise the careful watcher.
What you'll learn
What separates the two wave types is the direction the particles oscillate relative to the direction the energy travels, and that difference has a testable consequence: a transverse wave can be filtered down to one plane of oscillation, a longitudinal one cannot. Sound passes a grille at any orientation, while light through two crossed polarising filters is extinguished. Earthquakes send both — fast longitudinal P waves arrive first, slower transverse S waves follow and cannot cross the liquid outer core at all.
Key words
transverse wave
A wave in which particles oscillate at right angles to the direction the energy travels.
longitudinal wave
A wave in which particles oscillate along the direction the energy travels, making compressions and rarefactions.
Make a hypothesis first
Before you start: write down what you think will happen, and why.
Say your guess out loud — then find out if you were right.
Get ready
🧰 What you need
- slinky spring
- coloured sticky tape
- phone camera
- long clear floor
Get ready
⚠️ Safety first
- Hold the slinky firmly at both ends — a released spring snaps back hard.
Step 1 of 4 · Read
Think about what you just learned: say what "transverse wave" and "longitudinal wave" mean in your own words before you start.
Step 2 of 4 · Do
Send both wave types along a stretched slinky: flick it sideways for a transverse pulse, push and pull along its length for a longitudinal one. Film both in slow motion and mark on the film the direction the particles move against the direction the pulse travels.
Step 3 of 4 · Observe
Record what actually happened, including anything that did not match what you expected.
Step 4 of 4 · Record
Write a conclusion that answers the question this lesson opened with, and state your uncertainty.
Question 1 of 3
Question 2 of 3
Question 3 of 3
Mind = blown
🔬 The more you look, the more nature shows you.
Nice work!
You got 0 of 3 right.
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✨ More to explore
🌍 Where you see this in real life: This shows up in your everyday life more than you'd think.
🏆 Stretch challenge (try it this week): Try one experiment in real life this week — even a tiny one.
👨👩👧 For the dinner table: “What's the most surprising thing you learned today?”
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Ready?
Particle Motion Decides the Wave Type
Predict it first. Then prove yourself right (or wrong).
Full screen — no distractions
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Print the whole Waves track
All 8th Grade Waves lessons as a printable PDF, with worksheets and answer keys.