[quote]thanks for the great applets. However, I do not understand what is going on in "formation of wave
THere is a a spring, or set of springs at bottom of window. I do not understand your reference to two springs.
Thanks for any clarification you can offer.[/quote]

There are set of springs in the above simulation. The simulation want to point out
if every element have the same behavior but there is a delay between elements (delay is proportional to the distance between elements), then it is a wave (you will find a wave).

All the above springs have the same up and down vibration behavior. However, each one of them start the vibration at different time. So we find a wave moving to the right.

Check out the water wave, wave move in a spring, sound wave, electromagnetic wave, ... etc.
All of the above waves, there exists the same behavior in each space point. But there is a delay between neighbor points.

Webster's dictionary defines a wave as "a disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential, or temperature."

The most important part of this definition is that a wave is a disturbance or variation which travels through a medium. The medium through which the wave travels may experience some local oscillations as the wave passes, but the particles in the medium to not travel with the wave. The disturbance may take any of a number of shapes, from a finite width pulse to an infinitely long sine wave. [/quote]
The above message are quote from http://www.kettering.edu/~drussell/Demos/waves-intro/waves-intro.html