Practice question

**Superposition principle** states resultant displacement equals algebraic sum of individual waves, y = y₁ + y₂. For coherent waves with phase difference φ, resultant amplitude A = √(a₁² + a₂² + 2a₁a₂ cosφ), equal amplitudes give A = 2a cos(φ/2), constructive when φ = 2nπ, destructive when φ = (2n+1)π. At a node, displacement is zero, so there is no kinetic energy. The energy is entirely potential due to maximum strain, but no oscillation occurs. Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields It does not oscillate, illustrating frequency-length-speed interdependence and quantization by boundaries.