When a wave propagates in three dimensions instead of two, the amplitude of the wave remains the same. The amplitude of a wave represents the maximum displacement or intensity of the wave from its equilibrium position.
The change in dimensionality from 2D to 3D affects other properties of the wave, such as the spreading of the wave energy over a larger area. In three dimensions, the wavefront expands in a spherical manner, resulting in the redistribution of energy over the surface of a sphere. This means that the intensity of the wave decreases as the distance from the source increases.
However, the amplitude itself, which represents the maximum displacement or intensity of the wave, does not change due to the transition from 2D to 3D propagation. It remains constant as the wave moves through space, regardless of the number of dimensions involved.