Question

Why are the regions of compressions and rare fractions of sound waves formed?

• A. A sound wave undergoes diffraction behind obstacles.
• B. The reflected sound wave at a fixed end interferes with the incident wave.
• C. The longitudinal movement of air molecules produces pressure fluctuations.
• D. The speed of the sound wave changes as its travels through a medium.

Answer 1

The correct option is C The longitudinal movement of air molecules produces pressure fluctuations.

Longitudinal waves are made up of compressions and rarefactions. Compression happens when molecules are forced, or pressed, together. Rarefaction is just the opposite, it occurs when molecules are given extra space and allowed to expand. So, the longitudinal movement of air molecules produces pressure fluctuations which results in compression and rarefaction.