Waves and Sound

A wave is a disturbance that transfers energy from one place to another without permanently transferring matter. Transverse waves oscillate perpendicular to the direction of travel (light, water waves); longitudinal waves oscillate parallel (sound — compressions and rarefactions). Key wave quantities: amplitude (A) — maximum displacement from equilibrium (related to energy/loudness); wavelength (λ) — distance between two successive crests or compressions; frequency (f) — number of waves passing a point per second (Hz); period (T) — time for one complete wave (T = 1/f). Wave speed: v = fλ. Sound requires a medium — it cannot travel through a vacuum. The speed of sound in air ≈ 340 m/s; faster in liquids and solids. Pitch corresponds to frequency; loudness to amplitude. Echoes are reflections of sound; ultrasound (>20,000 Hz) is used in medical imaging. Light travels at 3 × 10⁸ m/s — faster in a vacuum than in any medium.