Stationary Waves & Resonance — A/L Physics

Stationary (Standing) Wave A wave pattern formed by the superposition of two identical waves travelling in opposite directions, resulting in nodes (points of zero displacement) and antinodes (points of maximum displacement). When a wave reflects from a fixed boundary, the incident and reflected waves interfere. At nodes, destructive interference occurs (displacement always zero); at antinodes, constructive interference occurs (displacement varies between ± 2A). Energy is not transferred along the medium—it is "trapped" in the pattern. Example: Plucking a guitar string creates a stationary wave with fixed ends.

Node A point on a stationary wave where the displacement is permanently zero. Nodes occur at positions where the two waves are always exactly out of phase (phase difference of π). For a string fixed at both ends, nodes always exist at the ends. The distance between successive nodes is λ/2. Intuition: The string does not move at these points—like a "dead spot."