Editing String vibration (section)

== Observing string vibrations ==

One can see the [[waveforms]] on a vibrating string if the frequency is low enough and the vibrating string is held in front of a [[CRT screen]] such as one of a [[television]] or a [[computer]] (''not'' of an analog oscilloscope).
This effect is called the [[stroboscopic effect]], and the rate at which the string seems to vibrate is the difference between the frequency of the string and the [[refresh rate]] of the screen. The same can happen with a [[fluorescent lamp]], at a rate that is the difference between the frequency of the string and the frequency of the [[alternating current]].
(If the refresh rate of the screen equals the frequency of the string or an integer multiple thereof, the string will appear still but deformed.)
In daylight and other non-oscillating light sources, this effect does not occur and the string appears still but thicker, and lighter or blurred, due to [[persistence of vision]].

A similar but more controllable effect can be obtained using a [[stroboscope]]. This device allows matching the frequency of the [[xenon flash lamp]] to the frequency of vibration of the string. In a dark room, this clearly shows the waveform. Otherwise, one can use [[bend (guitar)|bend]]ing or, perhaps more easily, by adjusting the machine heads, to obtain the same, or a multiple, of the AC frequency to achieve the same effect. For example, in the case of a guitar, the 6th (lowest pitched) string pressed to the third fret gives a G at 97.999&nbsp;Hz. A slight adjustment can alter it to 100&nbsp;Hz, exactly one octave above the alternating current frequency in Europe and most countries in Africa and Asia, 50&nbsp;Hz. In most countries of the Americas—where the AC frequency is 60&nbsp;Hz—altering A# on the fifth string, first fret from 116.54&nbsp;Hz to 120&nbsp;Hz produces a similar effect.