Practice question

**Wave classification** depends on particle vibration relative to propagation. Longitudinal waves have particle oscillation parallel to propagation, creating compressions and rarefactions as in sound in air; transverse have perpendicular oscillation. Tuning fork generates longitudinal sound because air cannot sustain shear. A medium must be rigid (have shear modulus) to support transverse waves and compressible (have bulk modulus) for longitudinal waves, properties typical of solids. Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields Rigidity, illustrating frequency-length-speed interdependence and quantization by boundaries.