A ray is a line that extends from the source and shows the wave's direction of propagation at any point along the line. Wavefronts and rays are parallel. The sun's rays are one type of ray, for instance. The sun is the starting point or point of origin, and its light rays travel endlessly throughout our solar system.
A wavefront is a line that represents all of a wave's in-phase components. A point source will produce waves with circular or spherical wave fronts, but a big, extended source will emit waves with wave fronts that are essentially flat, or plane. The shape of the wave front depends on the type of source. Consider the pattern of the water ripples created when a stone is thrown into a pond.
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A ray, which represents the direction in which the wave will propagate, is a perpendicular line drawn at any point on the wavefront.
A surface with a constant phase called a wavefront.
