# Pond Ripples

1. Oct 26, 2006

### Mindscrape

Here is the problem:
If a pebbel is tossed into a pond, a circular wave pulse propagates outward from the disturbance. If you look closely you will see a fine structure in the pulse consisting of surface ripples moving inward though the circular disturbance. Explain this effect in terms of group and phase velocity if the phase velocity of ripples is given by $$v_p = \sqrt{2 \pi S/ \lambda \rho}$$, Where S is the surface tension and p is the density of the liquid.

I am not really sure where to start. Should I find the envelope velocity and compare it to the high frequency velocity. I know it will have something to do with superposition, but fourier analysis seems like it is the wrong approach.