Colliding front patterns

In a uniform two-dimensional medium, such as a Petri dish, a wave emanating from a point produces a circular front, since it travels at the same velocity in all directions. If, as described in section 6.4, we have a system that generates repeated waves, we obtain a pattern of concentric circles, known as a target pattern. When two or more initiation sites are present, waves can collide, which results in annihilation of the colliding waves and can lead to patterns of considerable complexity. Typical examples in the BZ reaction are shown in Figure 6.6. 

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