# Wave motion

The movement of a distortion of a material where the individual elements of the material move back-and-forth, up-and-down or in a cyclic pattern is known as wave motion. For example when still water is disturbed by the fall of a stone, we can see water waves moving out in circles from where the stone was dropped. The pressure energy is the one that is travelling from one moving part to the other part of the water, forming a ripple.

The different types of waves related to this topic are stated below.

• Water waves are also known as mechanical waves.
• Sound waves are transmitted by vibrating particles of the medium involved.
• The oscillation of electric and magnetic fields occurs in case of electromagnetic waves.
• A wave is known as transverse wave when the particles of water move up and down in a perpendicular direction along the line the wave travels.
• Stationary or standing waves occur in tightly stretched wires between two points. When the wires are caused to vibrate, the waves cross each other along the wire forming stationary wave pattern.

The following graph of wave motion shows the different terms associated with the wave formation, with their brief description below. v = f λ

• The linear distance between successive crests is known as wavelength, represented as λ.
• The number of complete wave cycles generated in one second is known as frequency (f), and its unit is Hertz (Hz).
• The height of the crest from the undisturbed position is known as the amplitude.
• The distance moved by a crest in one second is known as speed (v).
• A point on the wave is known as trough, if the displacement of the medium at that point is at a minimum.
• A point along a standing wave where the wave has minimum amplitude is called as a node.
• A point along the medium that undergo maximum displacement during each vibrational cycle of the standing wave is called as an antinode.
• Interference or superposition occurs at points where two or more waves meet.
• The phase of the wave is defined as the distance between the first zero-crossing and the point in space which is defined as the origin. The waves are said to be in phase, when the two waves with the same frequency have a same phase. And the waves with the same frequency but different phases are said to be out of phase.

The greater the amplitude, the greater the energy carried. But the wave intensity is calculated from both frequency and amplitude. Some in-flight entertainment systems are built in with electronic equipment that detects noise vibrations from the engines and produces destructive interference patterns to reduce the noise.