# Wavefront of concentric Water Waves

What kind of wavefront does a water wave (ripples in water) have?

I'm confused since a wavefront is defined to be normal to the direction of wave propagation and joining all the particles in same phase, and I'm thinking of a plane parallel in which the wave (ripples) is transmitted , which doesn't satisfy the first criterion.

• Why do you say that the plane in which the wave is created doesn't satisfy the first criterion of being "normal to the direction of wave propagation"? In this picture the directions seem to be quite orthogonal: upload.wikimedia.org/wikipedia/commons/5/57/… Commented Mar 27 at 18:13
• @JosBergervoet are we talking about the same plane? I have edited the question to make it clearer. Commented Mar 27 at 18:18
• The wavefronts on water waves are lines not surfaces. Commented Mar 27 at 18:22
• If you restrict the wave purely to the surface, a "wave front" will be a line, not a plane, but actually the water is waving not only at the surface but also below the surface, so that could give you a vertical plane of constant phase, normal to the horizontal direction of propagation. If you don't go into the depth you still have a line of constant phase perpendicular to the propagation, like this: i.sstatic.net/ehvmF.jpg Commented Mar 27 at 18:28
• It depends when you look at it. youtu.be/4o48J4streE?si=u0aGu9x2qEEqxqOJ Commented Mar 28 at 16:27

In a water wave, molecules travel in a circle as the wave passes. The crest of the wave is where the molecules are at the top of their circle.

The surface where all molecules are at the top is a wavefront. You could also pick any other phase: at the bottom, or at $$37^o$$.

For a linear wave with a single frequency in deep water, the wave fronts are vertical planes. The amplitude of the circles get smaller with depth, until they are too small to measure.

In shallow water, waves slow. The back part catches up with the front. The wave gets taller and steeper until it breaks. Wave fronts still are linear in simple shorelines.

If you have multiple wavelengths, it gets more complex. Different frequencies travel at different speeds. Fourier analysis will resolve a complex wave into different components. You can assign wave fronts to each component. But I am not sure how you would define it for the sum.

Curved wave fronts also get messy. Looking at the picture, you can see general shapes that correspond to wave fronts. But there are places where crests end, or it isn't clear if there is a crest or not. It is hard to say what wave fronts would be there.