The wave refraction refers to the process by which the part of a wave in shallow water is slowed down to cause the wave to bend and tends to align itself with the underwater contours. In short, wave refraction means the bending of waves as they approach a shore.
The main significance of wave refraction lies in the fact that wave energy is redistributed. The wave energy becomes concentrated in some parts of the shoreline, while in other parts it is greatly reduced.
Let us imagine an irregular shoreline of bays; and headland! Deep water waves are parallel to each other whether they approach the shore directly or obliquely.
However, a wave reaches the shallow water off headlands sooner than the shallow water of a bay with the result that part of the wave reaching the headland or a promontory will become slow, and will be forced to break before that part which is approaching the bay.
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Since one part of the wave is slowed down before another part, the wave is bent or refracted. As a result, more energy is concentrated at the headland, so the waves are more destructive on the headlands than they are in the bays. In other words, wave erosion is more intensive on the headlands.
The debris produced by wave erosion at headlands is carried towards the bay where there is less energy. Because of the deposition of eroded material in the bays the shoreline irregularity is reduced. The headlands and promontories, due to intensive erosion, are pushed back, while the deposition in bays fills the indentations.