Formation of Waves on Stretched String

Taking a long string and tying one end to a wall, a single sharp jerk given to the free end sends a single, short-lived, bump-like disturbance travelling along the string -- this is called a wave pulse, since it lasts only a short duration and is not repeated. If, instead of a single jerk, the free end is shaken up and down continuously and repeatedly, the resulting disturbance is instead a continuous, sustained wave train rather than an isolated pulse; this is exactly how a plucked guitar string, or a rubber band stretched and plucked between two fingers, produces its sustained vibration. Standing at a beach and watching waves roll in and break on the shore is a large-scale, everyday example of the same underlying wave phenomenon, since ocean waves show the same repeating crest-and-trough pattern advancing toward the shore. This subsection thus distinguishes the two basic categories of disturbance a stretched string (or any elastic medium) can carry: a single isolated pul …