Wave refraction is a fundamental process where waves bend as they approach the shore, primarily due to changes in water depth. This bending causes wave fronts to align themselves more parallel to the coastline.
The Mechanism of Wave Refraction
The process of wave refraction is directly linked to how waves interact with the ocean floor as the water gets shallower near the shore.
The Role of Changing Depth
As a wave front moves from deep water towards the shore, the water depth decreases. This change in depth is critical because wave speed is dependent on depth, especially in shallower water.
Based on the provided information, "If a wave front approaches shore at an angle, the end of the wave front closest to shore will touch bottom before the rest of the wave." This physical interaction between the wave and the seabed in shallower areas is the starting point of refraction.
Differential Speed Causes Bending
Once part of the wave begins to touch the bottom, its speed is affected. The reference states, "This will cause that shallower part of the wave to slow down first, while the rest of the wave that is still in deeper water will continue on at its regular speed."
Imagine a wave crest approaching the shore at an angle. One side of the crest reaches the shallower water and the seabed first, slowing down significantly. The other side of the crest, still in deeper water, continues moving faster. This difference in speed across the wave front causes the wave to pivot or bend towards the slower side.
The Result: Waves Align with the Shore
The continuous bending effect as different parts of the wave encounter progressively shallower water causes the wave front to realign. Consequently, waves that might have approached the coast from various angles in deep water tend to arrive at the shoreline with their crests oriented nearly parallel to the coast. This explains why, regardless of the offshore wave direction, waves usually appear to break directly onto the beach.
Key Steps in Wave Refraction
Here's a simple breakdown of the process:
- A wave approaches the coastline, often at an angle.
- The part of the wave reaching shallower water encounters the seabed first.
- This interaction causes that section of the wave to slow down.
- The part of the wave still in deeper water continues at its original, faster speed.
- The difference in speed across the wave front causes the wave to bend.
- The wave continues to bend until its crest becomes increasingly parallel to the shoreline.
This process is crucial for understanding coastal erosion patterns, sediment transport, and even the design of coastal structures like breakwaters.
