Calcite, the most common form of natural calcium carbonate (CaCO3), a widely distributed mineral known for the beautiful development and great variety of its crystals.
A wavefront is a surface over which an optical wave has a constant phase. For example, a wavefront could be the surface over which the wave has a maximum (the crest of a water wave, for example) or a minimum (the trough of the same wave) value. The shape of a wavefront is usually determined by the geometry of the source.
Wave, ripple, breaker, surf refer to a ridge or swell on the surface of water. Wave is the general word: waves in a high wind. A ripple is the smallest kind of wave, such as is caused by a stone thrown into a pool: ripples in a brook. A breaker is a wave breaking, or about to break, upon the shore or upon rocks: the roar of breakers.