Molecules in a wave are _____, or squeezed together.

Molecules in a wave are _____, or squeezed together.

• A. rarefied
• B. compressed
• C. vibrating
• D. expanding

Answer: (B)

In a wave, especially a longitudinal one like sound, the particles move back and forth along the direction of travel, creating alternating regions where they are crowded together and where they spread apart. The phrase “squeezed together” describes the crowded region, which is the compression phase of the wave. So the molecules in a wave are compressed during compression. Think of it as the wave pulling particles closer together during compression and pushing them apart during rarefaction. The other ideas don’t fit because they describe motion or sparseness rather than the dense state: rarefied means less dense, expanding is a form of spreading, and vibrating describes motion, not the density state themselves.

In a wave, especially a longitudinal one like sound, the particles move back and forth along the direction of travel, creating alternating regions where they are crowded together and where they spread apart. The phrase “squeezed together” describes the crowded region, which is the compression phase of the wave. So the molecules in a wave are compressed during compression.

Think of it as the wave pulling particles closer together during compression and pushing them apart during rarefaction. The other ideas don’t fit because they describe motion or sparseness rather than the dense state: rarefied means less dense, expanding is a form of spreading, and vibrating describes motion, not the density state themselves.