A longitudinal wave is characterized by

A longitudinal wave is characterized by

• A. A wave that demonstrates only Sagittal imaging planes.
• B. Randomized particle motion.
• C. A constant acoustic velocity of 1,540 m/s.
• D. Particle motion occurring in the same direction as propagation.

Answer: (D)

In a longitudinal wave, the particles in the medium oscillate parallel to the direction the wave travels. As the wave propagates, the particles move back and forth along that same line, creating compressions and rarefactions that carry energy forward. That direct alignment of particle motion with the direction of propagation is the defining feature, so the best statement is that particle motion occurs in the same direction as the wave’s travel. The other ideas don’t fit this concept: imaging plane orientation (sagittal) is about how an image is cut, not how a wave moves; randomized particle motion would destroy the organized wave pattern; and a specific speed value (like 1,540 m/s) is a property of a medium, not the fundamental characteristic of longitudinal waves themselves, since wave speed varies with the medium.

In a longitudinal wave, the particles in the medium oscillate parallel to the direction the wave travels. As the wave propagates, the particles move back and forth along that same line, creating compressions and rarefactions that carry energy forward. That direct alignment of particle motion with the direction of propagation is the defining feature, so the best statement is that particle motion occurs in the same direction as the wave’s travel.

The other ideas don’t fit this concept: imaging plane orientation (sagittal) is about how an image is cut, not how a wave moves; randomized particle motion would destroy the organized wave pattern; and a specific speed value (like 1,540 m/s) is a property of a medium, not the fundamental characteristic of longitudinal waves themselves, since wave speed varies with the medium.