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.
As we know that wave is the periodical disturbance which is travelled through medium from particle to particle and if we observe the movement of wave then the phase is changed with time. There are some important terms related to wave like frequency, wavelength, wave number, velocity of wave etc.