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 REFRACTION. Most waves do not strike the shore directly, but rather meet it at an angle. When a wave approaches the coast in this manner, one end of the wave encounters shallow water first and slows down, while the rest of the waves is still in deeper water. Thus the part of the wave close to the shore slows down while the remainder continues to advance at a con tact speed.