To introduce a wave into a medium, the first particle is displaced or moved from its equilibrium or rest position. The particle might be moved upwards or downwards, forwards or backwards; but once moved, it is returns to its original equilibrium or rest position.
The wave medium is not the wave and it doesn't make the wave; it merely carries or transports the wave from its source to other locations.
the medium is a series of interconnected particles
The medium is composed of parts which are capable of interacting with each other. The interactions of one particle of the medium with the next adjacent particle allows the disturbance to travel through the medium.
Individual particles of the medium are only temporarily displaced from their rest position
There is always a force acting upon the particles which restores them to their original position. It is for this reason, that a wave is said to involve the movement of a disturbance without the movement of matter.
Any wave moving through a medium has a source.
Somewhere along the medium, there was an initial displacement of one of the particles.
the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding.
A wave on a rope will quickly reach the end of a cord, reflect and travel back in the opposite direction. Any reflected portion of the wave will then interfere with the portion of the wave incident towards the fixed end. This interference produces a new shape in the medium.
If a rope is held end to end and vibrated at just the right frequency , a wave pattern would be produced which assumes the shape of a sine wave and is seen to change over time.
When the proper frequency is used, the interference of the incident wave and the reflected wave occur in such a manner that there are specific points along the medium which appear to be standing still.
Because the observed wave pattern is characterized by points which appear to be standing still, the pattern is often called a standing wave pattern .
A standing wave pattern is a vibrational pattern created within a medium when the vibrational frequency of the source causes reflected waves from one end of the medium to interfere with incident waves from the source in such a manner that specific points along the medium appear to be standing still.
Such patterns are only created within the medium at specific frequencies of vibration; these frequencies are known as harmonic frequencies, or merely harmonics .
At any frequency other than a harmonic frequency, the interference of reflected and incident waves results in a resulting disturbance of the medium which is irregular and non-repeating.
two waves traveling in opposite directions along the same medium
The waves are interfering in such a manner that there are points of no displacement produced at the same positions along the medium, known as nodes ( N) .
There are also points along the medium which vibrate back and forth between points of large positive displacement and points of large negative displacement, known as antinodes ( AN) .
Nodes and antinodes should not be confused with crests and troughs.
When the motion of a traveling wave is discussed, a point of large maximum displacement is a crest and a point of large negative displacement is a trough. These represent points of the disturbance which travel from one location to another through the medium.
Nodes and antinodes are points on the medium.
Nodes and antinodes are not actually part of a wave.
A standing wave is not actually a wave but rather a pattern which results from the interference of two or more waves.