When a wave propagates through a medium like water, its energy is transferred from particle to particle. Each particle in the medium oscillates around its equilibrium position, passing on the energy to its neighboring particles. This process allows the wave to propagate.
In the case of water waves, the water molecules are the medium through which the wave travels. As the wave passes through the water, it causes the water molecules to move in a circular motion, with the energy of the wave being transferred from molecule to molecule.
The movement of water molecules slows down the wave due to the resistance and friction between the water molecules themselves. This frictional interaction absorbs some of the wave's energy and dissipates it as heat. Consequently, the wave gradually loses energy as it travels through the water.
However, even though the water slows down the wave, it doesn't completely stop it because there is still some residual energy left in the wave. This remaining energy allows the wave to continue propagating, albeit with reduced speed and amplitude. As the wave travels further and encounters more resistance from the water, it continues to lose energy until it eventually dissipates entirely.
It's important to note that without a medium, such as water, there would be no particles to transmit the wave's energy. In the absence of a medium, the wave would not be able to propagate at all. So, the presence of a medium is necessary for the wave to exist and propagate, even if the medium slows down and eventually absorbs the wave's energy.