Musical instruments, especially wind and stringed instruments, capitalise on the properties of standing waves to produce sound. In stringed instruments like guitars or violins, plucking or bowing the string creates a disturbance, producing waves that reflect off the ends and interfere with incoming waves, forming standing waves. The frequency of the standing wave determines the pitch of the sound. In wind instruments like flutes or clarinets, blowing creates waves within the air column inside the instrument. The length of the column, modified by opening or closing holes, changes the effective wavelength, producing different standing wave patterns and thus different pitches.

The distance between successive nodes or antinodes in a standing wave is directly related to the wavelength of the waves that created the standing wave. Specifically, the distance between two nodes or two antinodes is half the wavelength of the waves. This is because a full cycle of a wave (from crest to crest or trough to trough) encompasses both a node and an antinode. Understanding this relationship is crucial when examining standing waves in different media, as it can help deduce the original wavelength of the waves causing the standing wave pattern.

Yes, standing waves can form in any medium where waves can be generated and reflected. This includes water, metal plates, and even Earth's crust. In each medium, the principle is consistent: waves reflecting off boundaries interfere with incoming waves, leading to the formation of nodes and antinodes. An example outside of the typical classroom demonstration is "seiche waves" in enclosed or semi-enclosed bodies of water like lakes. A disturbance, possibly due to atmospheric changes or seismic activity, can lead to waves that reflect off the boundaries and interfere, creating standing waves within the body of water.

Standing waves appear stationary because of the superposition of two identical waves moving in opposite directions. As these waves interfere, they create alternating nodes and antinodes. The energy of the waves is effectively 'trapped' between these nodes and antinodes, causing oscillations around fixed points rather than allowing the energy to propagate forwards or backwards. While individual particles in the medium do oscillate and possess energy, this energy doesn't move forward in any direction, causing the entire system to appear static. In contrast, travelling waves move in a singular direction, transmitting their energy as they go.

The basic principle behind the formation of standing waves, whether on a string or in air, remains the superposition of two waves. However, the boundaries and medium differ significantly. For a string, the waves reflect off fixed ends, creating reflections that interfere with incoming waves. This gives rise to standing waves with nodes at the fixed ends. In contrast, for standing waves in air (as inside a pipe), the wave reflects off an open or closed end. An open end creates an antinode, while a closed end forms a node. Thus, the pattern and distribution of nodes and antinodes vary based on the medium and boundary conditions.