BioMedical Admissions Test (BMAT) Practice Test

Sound waves are classified as longitudinal waves because they propagate through a medium by causing the particles of that medium to oscillate parallel to the direction of the wave's energy transfer. In the case of sound waves, these oscillations create areas of compression and rarefaction in the medium (such as air, water, or solids), allowing the wave to travel through the medium.

Longitudinal waves contrast with transverse waves, in which the movement of the medium's particles is perpendicular to the direction of the wave. Understanding this distinction helps clarify why sound is categorized as a longitudinal wave.

While electromagnetic waves, such as light, do not require a medium and can propagate through a vacuum, they are transverse in nature. S-waves (shear waves) are also transverse waves, which only travel through solids. Waves on a string are a classic example of transverse waves, as the string's motion is perpendicular to the direction of the wave propagation. Thus, sound waves are the only example listed that fits the definition of a longitudinal wave.