Which definition matches compression in a longitudinal wave?

Which definition matches compression in a longitudinal wave?

• A. The part of a longitudinal wave where the particles are spread apart
• B. The crest
• C. The angle of incidence equals the angle of reflection
• D. The part of a longitudinal wave where the particles of the medium are close together

Answer: (D)

Compression in a longitudinal wave is the region where the particles of the medium are pressed close together as the wave passes. In longitudinal waves, the motion of the medium is parallel to the direction of travel, creating alternating regions of higher density (compressions) and lower density (rarefactions). So the description of particles being close together matches compression. The other descriptions describe something else: a region where particles spread apart is a rarefaction, a crest is from transverse waves, and a condition about angles describes reflection, which isn’t about compression.

Compression in a longitudinal wave is the region where the particles of the medium are pressed close together as the wave passes. In longitudinal waves, the motion of the medium is parallel to the direction of travel, creating alternating regions of higher density (compressions) and lower density (rarefactions). So the description of particles being close together matches compression. The other descriptions describe something else: a region where particles spread apart is a rarefaction, a crest is from transverse waves, and a condition about angles describes reflection, which isn’t about compression.