When water waves pass from deep water into shallow water, their direction changes.
Understanding Wave Refraction
The primary reason for this change in direction is a phenomenon known as refraction. Refraction occurs when a wave encounters a boundary between two different media or conditions, causing its speed to change.
As stated in the reference provided:
"Thus, if water waves are passing from deep water into shallow water, they will slow down. So as water waves are transmitted from deep water into shallow water, the speed decreases, the wavelength decreases, and the direction changes."
When a wave approaches the boundary between deep and shallow water at an angle, the part of the wave front that reaches the shallower water first slows down. The part of the wave front still in deeper water continues at its original speed for a moment longer. This difference in speed across the wave front causes the wave to bend, or refract, changing its direction of propagation.
Think of it like a car driving from pavement onto mud at an angle – the wheel hitting the mud first slows down, causing the car to pivot towards the mud. Similarly, water waves bend towards the shallower water if they are moving at an angle to the depth contours.
Associated Changes
Besides the change in direction, the transition from deep to shallow water also affects other wave characteristics:
- Speed: The speed of the water wave decreases significantly in shallow water.
- Wavelength: The wavelength of the wave also decreases.
- Height: Typically, the wave height increases as the wave slows down and compresses energy into a smaller volume, eventually leading to breaking waves if the water becomes shallow enough.
Here's a summary of how key wave properties change when moving from deep to shallow water:
| Property | Change (Deep -> Shallow) |
|---|---|
| Speed | Decreases |
| Wavelength | Decreases |
| Direction | Changes (Refracts) |
| Height | Increases (Typically) |
Understanding these changes is crucial in coastal areas, as refraction influences how waves approach the shoreline, determining wave energy distribution and impacting coastal erosion and deposition.
