12.1 Waves and Nature of Waves
As waves travel through a medium, they cause the particles within it to vibrate. These vibrations allow energy to be transferred from one particle to the next. However, the particles themselves do not move along with the wave. They simply oscillate around their original positions.
For example, when a twig is dropped into still water, ripples spread across the surface. These ripples carry energy outward, yet the water and the twig remain mostly in place.
A similar effect occurs with sound waves. When a guitar string is plucked, it creates vibrations that travel through the air as sound waves. The air particles do not move toward our ears; instead, they vibrate in place to pass the energy forward.
lightbulbWaves can transfer energy from one place to another without transferring matter.
The same principle is illustrated by vibrations in a spring. When one end of a stretched spring is pushed and released, longitudinal waves move through the spring. The spring develops regions of compression (where the coils are close together) and rarefaction (where the coils are spread out). These compressions and rarefactions travel along the spring, showing how energy is transmitted without the entire spring moving forward.