The correct option is (c).
Explanation
Sound waves are longitudinal waves characterized by the propagation of compressions and rarefactions in a medium. These waves are defined by variables such as frequency, amplitude, and speed. Amplitude refers to the magnitude of the maximum disturbance in the medium on either side of the mean value.
Statement-wise Analysis:
- Statement 1 is Incorrect: The amplitude of a sound wave is conventionally represented by the letter A. The letter Z is typically used to denote acoustic impedance or atomic number in other contexts.
- Statement 2 is Correct: Since sound waves propagate as variations in the medium's density and pressure, the disturbance can be measured in terms of these physical quantities. Therefore, the unit of amplitude corresponds to the unit of the quantity being measured, which is either density (kg/m³) or pressure (Pascal).
- Statement 3 is Correct: The amplitude corresponds to the energy of the wave. It depends directly on the force with which the source object is made to vibrate. A stronger force causes a larger displacement from the equilibrium position, resulting in a higher amplitude and a louder sound.
Key Takeaway:
Amplitude determines the loudness of a sound. It represents the maximum variation in density or pressure from the equilibrium state and is directly proportional to the force applied to generate the vibration.