Mechanical Waves

There are only two fundamental mechanisms for transporting energy and momentum: a streaming of particles and a flowing of waves. And even these two seemingly opposite conceptions are subtly intertwined - there are no waves without particles and no particles without waves. (From the latter we only get a glimpse, when we talk about some specific properties of light.) In general a wave is a moving self-sustained disturbance of a medium, and that medium can be either a field (e.g. the gravitational field) or a substance (a solid or fluid). Here, the focus is on waves in a material media, and these are known as mechanical waves . When a wavetrain of any kind is created in some real, finite medium (whether a string, a drum or the earth itself), it will propagate outward until it encounters a end or boundary. There, some fraction of the wave-energy will usually be reflected backward, and if the original disturbance is sustained, the medium will quickly fill with waves traveling back and forth over one another. These disturbances will combine or interfere to form a steady-state distribution of energy known somewhat paradoxically as Standing or Stationary Waves We also need to consider how to sustain oscillations of a system and consider forced oscillations and Resonance

Ch. Elster
Oct 16 14:27:03 EDT 2020