The conversion of an incident pressure wave to an electrical signal is the:

• A. Curie effect
• B. Piezoelectric effect
• C. Doppler effect
• D. Snell effect

Answer: (B)

Piezoelectricity enables the conversion of mechanical pressure into an electrical signal. When an incident pressure wave compresses or stretches a piezoelectric material, its non-centrosymmetric crystal structure causes charge separation and a voltage appears across the material. In ultrasound transducers, this means the incoming acoustic pressure directly generates an electrical signal that can be detected and measured, with the signal strength proportional to the pressure (and thus to the wave’s information). The reverse piezoelectric effect is also used to emit waves by applying an electrical signal to the crystal.

The other effects don’t describe this conversion. The Doppler effect involves a shift in frequency due to motion, not turning pressure into electricity. Snell’s law (often called refraction) explains how waves change direction at boundaries, not transduction. Curie-related concepts relate to polarization and phase transitions, not the direct acoustic-to-electrical conversion in a receiver.