Longitudinal waves involve particle vibration parallel to wave direction

Steps:

• Recall that longitudinal waves have oscillations parallel to propagation, unlike transverse waves where they are perpendicular.
• Identify wave types: electromagnetic waves (gamma, light, X-rays) are transverse; sound waves are longitudinal.
• Note ultrasound is high-frequency sound waves, propagating through media like air or tissue.
• Match ultrasound to longitudinal category based on sound wave properties.

Why C is correct:

• Ultrasound waves are mechanical sound waves where particles vibrate parallel to propagation, fitting the longitudinal wave definition.

Why the others are wrong:

• A. Gamma rays are electromagnetic waves with perpendicular electric/magnetic oscillations, making them transverse.
• B. Light waves are electromagnetic, propagating transversely through perpendicular vibrations.
• D. X-rays are electromagnetic radiation, transverse like visible light.

Final answer: C