Circular wave and parallel wave

My name is: (also known as plane wave) parallel wave those mountains and valleys of the wave is a straight line.In addition, circular wave those in the form of a circle: My name is (also known as spherical wave). There is something like that shown in the following diagram: The circular wave and parallel wave.

Prime element wave

Vibration of the very beginning that occurred in wave source, will transmitted around Become a circular first wave.Each part of this circular Since the vibration, then, each point becomes the new wave source, I will send out the vibration, respectively.
I called a prime element wave a wave of circular waves emanating from each point on the wave like this.In addition, it is known as Huygens' principle the idea to become wavefront tie the surface that are common on the basis of the original wave.

Diffraction

Wave passes through the gap and spreads in a circle.In this way, I called the diffraction properties sneaking behind the obstacle.Diffracted wave is easy to sneak behind the obstacles and to reduce the gap, but it will not wrap behind the obstacles and to increase the gap.