What is a compression wave?

What is a compression wave?

• A. The wave has crests and troughs
• B. Matter moves back and forth along the direction the wave travels
• C. The medium does not move
• D. The wave travels faster in air than in water

Answer: (B)

Compression waves are longitudinal waves in which the particles of the medium vibrate parallel to the direction the wave travels. As the wave moves, the medium is alternately squeezed together and spread apart, creating regions of higher density (compressions) and lower density (rarefactions). That back-and-forth motion along the travel direction is what defines this type of wave, and explains why sound waves in air are a common example. The idea of crests and troughs belongs to transverse waves, where motion is perpendicular to the travel direction. The statement that the medium doesn’t move isn’t true for compression waves, since the particles oscillate as the wave passes. And the fact that a wave travels faster in one medium than another doesn’t define a compression wave—it’s about how fast waves propagate in different materials, not the wave’s type.

Compression waves are longitudinal waves in which the particles of the medium vibrate parallel to the direction the wave travels. As the wave moves, the medium is alternately squeezed together and spread apart, creating regions of higher density (compressions) and lower density (rarefactions). That back-and-forth motion along the travel direction is what defines this type of wave, and explains why sound waves in air are a common example. The idea of crests and troughs belongs to transverse waves, where motion is perpendicular to the travel direction. The statement that the medium doesn’t move isn’t true for compression waves, since the particles oscillate as the wave passes. And the fact that a wave travels faster in one medium than another doesn’t define a compression wave—it’s about how fast waves propagate in different materials, not the wave’s type.