Practice question

**Doppler effect** describes apparent frequency shift due to relative motion between source and observer, f' = f·v/(v ∓ v_s) for source motion, f' = f·(v ± v_o)/v for observer motion, upper signs for approach increasing observed frequency. Motion towards observer compresses wavelength raising f'. Speed of sound in a gas increases with temperature ( v ∝ √(T) ), significantly altering its propagation, while frequency remains source-dependent and amplitude may vary less directly. Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields Speed, illustrating frequency-length-speed interdependence and quantization by boundaries.