The number of complete oscillations per unit time.
Explanation
Sound propagates through a medium as a mechanical wave characterized by periodic disturbances. To describe these waves physically, specific parameters such as frequency, period, wavelength, and amplitude are used to quantify the motion of particles in the medium.
Detailed Analysis:
- The time taken for one complete oscillation. is Incorrect: The time taken for one complete oscillation or cycle is defined as the Time Period ($T$). It is mathematically the reciprocal of frequency ($T = 1/f$).
- The number of complete oscillations per unit time. is Correct: Frequency ($f$ or $\nu$) is defined as the number of complete oscillations (or cycles) occurring per unit of time. It is measured in Hertz (Hz), where 1 Hz represents one oscillation per second.
- The distance between two consecutive compressions. is Incorrect: The distance between two consecutive compressions (or rarefactions) in a longitudinal wave, or two consecutive crests in a transverse wave, is defined as the Wavelength ($\lambda$).
- The maximum disturbance in the medium. is Incorrect: The maximum displacement or disturbance of a particle from its mean equilibrium position is defined as the Amplitude ($A$). This determines the loudness of the sound.
Key Takeaway:
Frequency measures the rate of oscillation ($f = 1/T$), while wavelength measures the spatial length of a cycle, and amplitude measures the magnitude of the disturbance.