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

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

Answer: (B)

The piezoelectric effect explains how an ultrasound transducer turns an incoming pressure wave into an electrical signal. When the acoustic pressure from tissue strikes the piezoelectric crystal, the mechanical stress causes the crystal to deform slightly, producing electric charges that generate a voltage signal. This signal is then sent to the receiver and processed into an image. The same material can be driven by electricity to vibrate and emit ultrasound, which is the converse piezoelectric effect. The other terms don’t describe this energy conversion: Doppler relates to frequency shifts from motion, Snell’s law to refraction at boundaries, and Curie-related concepts pertain to temperature-dependent ferroelectric properties rather than converting a pressure wave into an electrical signal.