Which of the following best describes how to measure the amplitude $A$ of a longitudinal wave?

• A. Measure the maximum displacement $x\_\max$ of particles from their equilibrium position along the direction of wave propagation.
• B. Measure the time $T$ it takes for a particle to complete one oscillation.
• C. Measure the distance $b$ between two consecutive compressions.
• D. Measure the speed $v$ at which the wave travels through the medium.

Answer: (A)

Verified step by step guidance

1. Understand that a longitudinal wave consists of particles oscillating back and forth along the direction of wave propagation, creating regions of compression and rarefaction.
2. Recall that the amplitude \( A \) of a wave is defined as the maximum displacement of particles from their equilibrium (rest) position during oscillation.
3. Identify that in a longitudinal wave, this displacement occurs along the same direction as the wave travels, so the amplitude corresponds to the maximum distance particles move from their normal position along the wave path.
4. Note that other quantities like the time period \( T \), wavelength (distance between compressions), and wave speed \( v \) describe different properties of the wave, not the amplitude.
5. Therefore, to measure the amplitude \( A \) of a longitudinal wave, you measure the maximum displacement \( x_{max} \) of particles from their equilibrium position along the direction of wave propagation.