Definition of mechanical wave
The propagation of mechanical vibration in a medium is called a mechanical wave. Mechanical waves and electromagnetic waves have similarities and differences. Mechanical waves are generated by mechanical vibrations, and electromagnetic waves are generated by electromagnetic oscillations. The propagation of mechanical waves requires a specific medium. The propagation speed in different media is also different, and it cannot be transmitted in a vacuum at all. Electromagnetic waves (such as light waves) can propagate in a vacuum; mechanical waves can be shear waves and longitudinal waves, but electromagnetic waves can only be shear waves; many physical properties of mechanical waves and electromagnetic waves, such as refraction and reflection, are consistent, and the physical quantities that describe them are also identical. Common mechanical waves are: water waves, acoustic waves, and seismic waves.