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.
A wave is defined as a disturbance which is moved medium; for example, the wave of the ocean moves in medium water and we can see the movement of wave crest from one side to the other side in a given time period. The motion of objects is described in terms of speed which shows the fastness of the object.