What is the key principle of how a condenser microphone works?

The correct answer is grounded in the fundamental operation of condenser microphones, which rely on the principle of capacitance. A condenser microphone consists of two plates that form a capacitor. One of these plates vibrates in response to sound waves, changing the distance between the plates. When sound pressure varies, it causes the diaphragm (one of the plates) to move, which leads to variations in capacitance. The resulting changes in capacitance are then converted into an electrical signal, accurately capturing the audio input.

This principle highlights the sensitivity of condenser microphones, as they can detect the nuances in sound pressure, making them ideal for capturing speech and musical instruments. The emphasis on capacitance distinguishes this type of microphone from dynamic microphones, which operate through the movement of a coil in a magnetic field, thus making option B the most accurate representation of how a condenser microphone works.