Which statement correctly describes a property of longitudinal waves?

Which statement correctly describes a property of longitudinal waves?

• A. They have compressions
• B. They have crests and troughs
• C. They vibrate perpendicular to the direction of travel
• D. They do not require a medium

Answer: (A)

Longitudinal waves move the particles of the medium in the same direction as the wave travels, creating alternating regions of higher and lower density called compressions and rarefactions. The presence of compressions is a defining feature of this type of wave, so saying they have compressions correctly describes a property of longitudinal waves. By contrast, crests and troughs are characteristics of transverse waves, where the motion is perpendicular to the direction of travel. Also, longitudinal waves (like sound in air) generally require a medium to propagate, so the idea that they do not require a medium isn’t accurate for these waves.

Longitudinal waves move the particles of the medium in the same direction as the wave travels, creating alternating regions of higher and lower density called compressions and rarefactions. The presence of compressions is a defining feature of this type of wave, so saying they have compressions correctly describes a property of longitudinal waves. By contrast, crests and troughs are characteristics of transverse waves, where the motion is perpendicular to the direction of travel. Also, longitudinal waves (like sound in air) generally require a medium to propagate, so the idea that they do not require a medium isn’t accurate for these waves.