What constitutes one cycle in the context of sound waves?

• A. One rarefaction and one compression
• B. One reflection and one absorption
• C. One amplitude and one frequency
• D. One echo and one sound

Answer: (A)

One cycle in the context of sound waves refers to the complete sequence of events that occurs as a sound wave propagates. This cycle includes one compression and one rarefaction. Compression is the phase where air particles are pushed together, leading to increased pressure, while rarefaction is the opposite phase where the air particles are pulled apart, resulting in decreased pressure. Together, these two phases create a full cycle of pressure changes in the medium through which the sound is traveling, effectively producing a sound wave.

The other options do not accurately define a cycle in sound waves. Reflection and absorption are processes that can affect sound waves but do not describe one complete cycle of the wave itself. Similarly, amplitude and frequency are characteristics of sound waves rather than individual elements of a cycle. An echo is a reflection of sound and not part of the wave's cycle. Thus, option A stands out as the only choice that accurately defines one cycle in terms of sound wave mechanics.