The correct option is (c).
Explanation
Sound is a mechanical wave produced by vibrating objects. As it propagates through a medium, the particles of the medium oscillate about their equilibrium positions. The characteristics of the sound, such as loudness, are determined by the properties of this oscillation, specifically the amplitude.Statement 1 is Correct: The amplitude of a wave is defined as the magnitude of the maximum displacement or disturbance of the particles of the medium from their mean (equilibrium) position. In a graphical representation of a sound wave, this corresponds to the peak height of a crest or the depth of a trough relative to the central axis.
Statement 2 is Incorrect: As a sound wave moves away from its source, the energy it carries spreads out over an increasingly larger area (spherical wavefronts). Additionally, the medium absorbs some of the energy (damping). Consequently, the amplitude of the wave decreases with distance, causing the sound to become fainter, rather than increasing.
Statement 3 is Correct: The loudness of a sound is directly related to the amount of energy carried by the wave. Loudness is proportional to the square of the amplitude of the vibration ($L \propto A^2$). Therefore, a wave with a larger amplitude possesses higher energy and is perceived as a louder sound.
Key Takeaway: Amplitude determines the loudness of a sound, whereas frequency determines its pitch. Amplitude diminishes as the distance from the source increases due to the spreading of energy and attenuation.