S4.10.3 For the adult
Waves on water
Priya's ripples run from deep water onto a shallow part of the tray. What happens to them?
What this chapter teaches
The speed of ripples comes from v = fλ, with the wavelength measured across several gaps. Water waves slow down in shallow water, and their frequency does not change, so the wavelength shortens. At a slanted edge they bend towards the normal in the slower part.
Three questions to ask
There is no one right wording. Listen for the idea.
- Five wavefronts have 28 cm across them. How would you find the wavelength?
- What happens to the frequency, the speed and the wavelength of a water wave when it enters shallow water?
- Why does a wave that meets a shallow part at a slant change direction?
After the chapter, the learner can
- Measure the speed of ripples in a tray of water
- Explain how water waves slow down and bend in shallow water
What they copy into their notebook
v = fλ. Measure λ across several gaps: fronts − 1. Shallow water slows waves. f stays the same, so λ shortens and the wave bends towards the normal.