What is the definition of a sound wave?

• A. A transverse disturbance in the magnetic field.
• B. A static pressure wave.
• C. A chemical vibration in materials.
• D. A longitudinal pressure disturbance that propagates through a medium.

Answer: (D)

Sound waves are mechanical disturbances produced by vibrating objects that propagate by pushing and pulling neighboring particles. As the disturbance travels, it creates alternating regions of higher and lower pressure, known as compressions and rarefactions, moving through a medium such as air, water, or solids. This makes sound a longitudinal wave, with particle motion parallel to the direction of travel. It is a time-varying pressure change, not a static one, and it requires a material medium to carry the wave. The definition that fits this best is a longitudinal pressure disturbance that propagates through a medium.