WAEC Physics 2015 Paper

Concept:A vibrating air column produces a stationary (standing) wave, whose nodes are points of zero displacement.Explanation:When an air column vibrates, the incident and reflected waves superpose to form a stationary wave.These stationary waves have alternate nodes and antinodes that remain fixed in space.The distance between two consecutive nodes is always a fixed fraction of the wavelength.A full wavelength is made of two adjacent loops.Each loop is separated from the next by a node.Therefore, moving from one node to the next corresponds to travelling through half a loop pair, i.e., half a wavelength.Mathematically, consecutive nodes are spaced by $\frac{\lambda}{2}$, where $\lambda$ is the wavelength of the sound wave.This is true for all stationary waves, including those in air columns.Thus, regardless of whether the air column is open or closed, the node-to-node distance remains $\frac{\lambda}{2}$.Answer:B. half of the wavelength