Waves & how they move
Develop a model of waves to describe patterns in terms of amplitude and wavelength, and understand that waves can cause objects to move
What a learner can do afterwards
- Describe a wave using the terms amplitude (height) and wavelength (distance between peaks)
- Compare energy using amplitude for otherwise comparable waves in the same material and setup
- Model wave patterns using a slinky, rope, or water and describe what they observe
1 · Read
A wave is a disturbance that travels, not a drawing. Amplitude is the greatest movement from the resting position. For an up-and-down rope wave, measure from the resting line to a peak. A repeating wave has peaks one after another. A single bump on its own does not have a next peak for measuring wavelength. Shaking rate is how often the hand shakes. Tension is how tightly the rope is pulled.
Wavelength is the distance along a repeating wave from one peak to the next peak. Shake a stretched spring sideways repeatedly to make travelling bumps. Watch the bumps move along it. Measure the distance between neighbouring peaks with a ruler, not along the curved spring.
Mia keeps the rope, tension and shaking rate unchanged. Moving her hand farther from rest increases amplitude; moving it less decreases amplitude. When nothing else changes, larger amplitude carries more energy. Amplitude alone cannot tell you which waves carry more energy in different setups.
In a simplified water-wave model, a floating cork follows the surface up and down while the pattern passes. Larger amplitude means more vertical movement. The cork mainly bobs instead of travelling with the pattern. Real water waves can also involve horizontal movement and drift.
Wider gaps between neighbouring peaks mean longer wavelengths. Three consecutive peaks span two wavelengths. Measure from the first peak to the third, then divide by two to find one wavelength.
Height above rest describes amplitude. Spacing between neighbouring peaks describes wavelength. Taller peaks mean larger amplitude; wider spacing means longer wavelength. Confusing height with spacing mixes up the measurements.
Amplitude measures movement from rest. Wavelength measures spacing in a repeating wave. For otherwise comparable waves in the same setup, larger amplitude means more energy.
Original extra questions and reading passage written for this learning dataset.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
14 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.