The process of sound propagating by back and forth movement of particles within the medium is called what?

• A. Propagation
• B. Diffraction
• C. Vibration
• D. Reflection

Answer: (C)

Sound moves through a medium because the particles oscillate back and forth around their rest positions. That back-and-forth motion of particles is called vibration, and it’s how the energy of the sound wave is transferred from one particle to the next, forming the traveling wave. The other terms describe different aspects: propagation refers to the overall spread of the wave, diffraction is bending around obstacles, and reflection is the wave bouncing off a surface. Since the description focuses on the local oscillation of particles, vibration is the best fit.