Which description best characterizes an ultrasound wave in human tissue?

• A. Radioactive wave
• B. Transverse rarefactional wave
• C. Electromagnetic wave
• D. Mechanical longitudinal wave

Answer: (D)

Ultrasound waves in human tissue are mechanical longitudinal waves because they propagate through a medium by compressions and rarefactions, with particle motion parallel to the direction of travel. They rely on the medium’s density and elasticity to carry the wave, and they are not electromagnetic or radioactive. Among the options, describing it as a mechanical longitudinal wave best fits how ultrasound actually moves through tissue. The other descriptions mix concepts that don’t apply here: a transverse wave would have particle motion perpendicular to propagation, which isn’t how ultrasound behaves in tissue; electromagnetic waves are not mechanical pressure waves in material media; and radioactive refers to nuclear decay, not a wave type.