A Level Physics Practice Exam 2026 - Free A Level Physics Practice Questions and Study Guide

The correct answer is that interference occurs when two waves meet. This phenomenon arises when two or more waves overlap in space and combine their effects. The principle of superposition states that when waves meet, the resultant wave function is the sum of the individual wave functions at each point in space. This can lead to constructive interference, where the resultant wave is larger due to the addition of wave amplitudes, or destructive interference, where the resultant wave can be smaller or even cancel out completely if the waves are out of phase.

The concept of superposition is closely related to interference, but interference describes the observable effect of the waves interacting with one another. Thus, while superposition is the underlying principle that describes how the waves mathematically combine, interference is the observable outcome when the waves physically meet and overlap.