Waves can be described as oscillations or vibrations, which are back-and-forth movements.
All waves transfer energy from one place to another, but they do not transfer matter.
There are two types of waves:
In a transverse wave, the oscillations are perpendicular (at a 90° angle) to the direction of wave travel.
Most waves we think of are transverse waves, which include all electromagnetic waves. Some examples of transverse waves are:
In a longitudinal wave, the oscillations are parallel to the direction of wave travel.
In a longitudinal wave, there are regions of compression and rarefaction, as you can see in the diagram above. Some examples of longitudinal waves are:
The wave diagram shows the peak and trough of the wave.
Peak – The highest point above the midpoint.
Trough – The lowest point below the midpoint.
The horizontal line, often called the baseline or equilibrium, represents the midpoint of the wave.
An oscilloscope can be used to display and analyse the waveform of longitudinal waves.
For example, when studying a sound wave (a longitudinal wave) using an oscilloscope, the waveform is displayed similarly to a transverse wave.