- AAll points are in the same phase.
- BThere is a pair of points in opposite phase.
- CThere is a pair of points with phase difference $(\frac{\pi}{2})$.
- DThere is no relation between the phases.
Explanation:
A wavefront is the locus of points characterized by propagation of position of the same phase:
a propagation of a line in 1D, a curve in 2D or a surface for a wave in 3D.
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