Which of the following is an example of a longitudinal wave?

• A. Light wave in vacuum
• B. Radio wave
• C. Sound wave in air
• D. Water wave on the surface of a pond

Answer: (C)

Verified step by step guidance

1. Understand the difference between longitudinal and transverse waves. In a longitudinal wave, the particle displacement is parallel to the direction of wave propagation, while in a transverse wave, the particle displacement is perpendicular to the direction of wave propagation.
2. Analyze each option: Light waves and radio waves are electromagnetic waves, which are transverse waves because their electric and magnetic fields oscillate perpendicular to the direction of propagation.
3. Water waves on the surface of a pond are primarily transverse waves because the water particles move up and down while the wave travels horizontally.
4. Sound waves in air are longitudinal waves because the air particles oscillate back and forth along the same direction that the sound wave travels, creating compressions and rarefactions.
5. Therefore, the example of a longitudinal wave among the options is the sound wave in air.