In general, the amplitude of a wave does not decrease as it propagates through empty space. In a vacuum or a region with no significant obstacles or interactions, a wave will maintain its amplitude as it travels. This property is known as the conservation of wave amplitude.
However, it's important to note that in real-world scenarios, waves can experience various factors that can lead to a decrease in their amplitude over distance. These factors include:
Geometrical spreading: For waves that spread out in a three-dimensional space, such as sound or light waves, the wavefront expands as it propagates. The same amount of energy gets distributed over a larger area, resulting in a decrease in the wave's intensity (energy per unit area) and amplitude as you move farther away from the source.
Absorption: Some materials or media can absorb energy from a wave as it passes through. This absorption leads to a reduction in the wave's amplitude. For example, as sound travels through air, it can be absorbed by objects or converted into heat energy, causing the sound's amplitude to decrease.
Scattering: When waves encounter small particles or irregularities in a medium, they can scatter in various directions. This scattering can cause a redistribution of energy, leading to a decrease in the wave's amplitude in certain directions.
Attenuation: Certain types of waves, such as electromagnetic waves traveling through a medium like water or air, can experience attenuation. Attenuation refers to the gradual reduction in the wave's intensity and amplitude due to factors like absorption, scattering, and dispersion within the medium.
Therefore, while waves can experience a decrease in amplitude under certain conditions and in real-world situations, in the absence of such factors, the amplitude of a wave will generally remain constant as it travels through space.