OCR A-Level Geography H481
Coastal Landscapes
Glaciated Landscapes
Dryland Landscapes
Earth’s Life Support Systems
Changing Spaces; Making Places
Trade in the Contemporary World
Global Migration
Human Rights
Power and Borders
Climate Change
Disease Dilemmas
Exploring Oceans
Future of Food
Hazardous Earth
Geographical Skills
Coastal Landscapes
Constructive and destructive waves, and how waves break
- 3 things to know
- Component 01
Overview
Recall questions on how waves change in shallow water and when they break, wave steepness and orbital motion, swash and backwash, spilling, plunging and surging breakers, the features and effects of constructive and destructive waves, berms, and wave refraction around a headland.
What you need to know
Answer each one before you reveal it.
Why does the orbit of the water particles become elliptical close to the shore?
Define swash and backwash.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Explain what happens to a wave as it moves into shallow water.
Model answer
Friction with the sea bed slows the base of the wave, so its wavelength shortens, it steepens and its height increases until it becomes unstable.
- 2
At what water depth does a wave usually break?
Model answer
When the depth falls to roughly 1.3 times the height of the wave.
- 3
What is wave steepness, and at what value does a wave break?
Model answer
It is the ratio of wave height to wavelength, and a wave becomes unstable and breaks once that ratio exceeds about 1:7.
- 4
Describe the circular orbital motion of water in a deep water wave.
Model answer
Each water particle travels in a closed circle as the wave passes, so the energy moves forward while the water itself stays largely in the same place.
- 5
Why does the orbit of the water particles become elliptical close to the shore?
Model answer
The sea bed obstructs the bottom of the orbit, flattening the circle into an ellipse and finally into a to-and-fro movement.
- 6
Define swash and backwash.
Model answer
Swash is the water rushing up the beach after a wave has broken, and backwash is the water draining back down the beach under gravity.
Other ways to work this
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