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.
(General Physics) physics. a. a property of a physical system characterized by the behaviour of the sign of its wave function when all spatial coordinates are reversed in direction. The wave function either remains unchanged (even parity) or changes in sign (odd parity)