What is the principle of superposition as applied to waves?

The principle of superposition states that when two or more waves meet, the resultant displacement is the sum of the individual displacements.

This principle applies to all types of waves, including mechanical waves like sound waves and electromagnetic waves like light waves. When two waves meet, they pass through each other and their amplitudes add together at each point in space. If the waves are in phase (i.e. their crests and troughs align), they will reinforce each other and create a larger amplitude. If they are out of phase (i.e. their crests and troughs do not align), they will cancel each other out and create a smaller amplitude.

The principle of superposition also applies to waves that are travelling in opposite directions. When two waves with the same amplitude and frequency but travelling in opposite directions meet, they create a standing wave. This is a wave pattern that appears to be standing still, even though the individual waves are still moving. The points where the amplitude is zero are called nodes, and the points where the amplitude is at a maximum are called antinodes.

The principle of superposition is a fundamental concept in wave theory and is used to explain many phenomena, from interference patterns in light waves to the resonance of musical instruments. Understanding this principle is essential for A-Level Physics students studying waves and their properties.