Melde's experiment
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Melde's experiment is a scientific experiment carried out by the German physicist Franz Melde on the standing waves produced in a tense cable originally set oscillating by a tuning fork, later improved with connection to an electric vibrator. This experiment attempted to demonstrate that mechanical waves undergo interference phenomena. In the experiment, mechanical waves traveled in opposite directions from immobile points, called nodes. These waves were called standing waves by Melde since the position of the nodes and loops (points where the cord vibrated) stayed static.
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[edit] History
Wave phenomena in nature have been investigated for centuries, some being some of the most controverted themes in the history of science, and so the case is with the wave nature of light. In the 17th century, Sir Isaac Newton described light through a corpuscular theory. The English physicist Thomas Young later contrasted Newton's theories in the 18th century and established the scientific basis upon which rest the wave theories. At the end of the 19th century, at the peak of the second industrial revolution, the creation of electricity as the technology of the era offered a new contribution to the wave theories. This advance allowed Franz Melde to recognize the phenomena of wave interference and the creation of standing waves. Later, the Scottish physicist James Clerk Maxwell in his study of the wave nature of light succeeded in expressing waves and the electromagnetic spectrum in a mathematical formula.
[edit] Principle
A string undergoing transverse vibration illustrates many features common to all vibrating acoustic systems, whether these are the vibrations of a guitar string or the standing wave nodes in a studio monitoring room. In this experiment the change in frequency produced when the tension is increased in the string – similar to the change in pitch when a guitar string is tuned – will be measured. From this the mass per unit length of the string / wire can be derived.
Finding the mass per unit length of a piece of string is also possible by using a simpler method – a ruler and some scales – and this will be used to check the results and offer a comparison. Failed to parse (lexing error): f=1/2L√Mg/μ
[edit] Experimental demonstration
[edit] Graphic analysis
[edit] Dependence on the tension-longitude of a wave
[edit] Dependence on the tension-longitude of a wave in a square
[edit] Frequency of standing waves
[edit] Influence of Melde's experiment
Although Melde's experiment allowed the identification and study of standing waves, its influence was not limited to this field. Standing waves are a phenomenon with very important applications in the field of acoustics, and in the phenomena of reflection and constructive interference of these waves.
[edit] Sonar
Sonar is basically a navigation and localization system similar to radar. However, instead of emitting radio signals, it emits ultrasonic impulses instead. After the transmitter sends out a bunch of ultrasonic impulses, they hit an object and bounce off it. They then form an echo (a standing wave) that is picked up through the receiver.
Some animals have a natural sonar. One such case of this is dolphins. They use it to keep track of where they are in turbulent waters and to hunt safely.
Bats use it to figure out where they are and to hunt in the darkness, emitting short, ultrasonic vibrations that bounce off the walls of their homes, objects in a place that isn't familiar, or their prey.
[edit] Telecommunications
[edit] Music
- Main aritcle: Wind instruments
