The thickness of a PZT element is typically equal to what fraction of the emitted wavelength?

The thickness of a PZT element is typically equal to what fraction of the emitted wavelength?

• A. 1/2
• B. 1/4
• C. 1
• D. 3/4

Answer: (A)

In thickness-mode transducers, resonance occurs when the crystal thickness corresponds to half the acoustic wavelength inside the crystal. The emitted wavelength is λ = v/f, with v the speed of sound in the crystal and f the drive frequency. For fundamental resonance, the crystal thickness d satisfies d = λ/2, so the thickness is about one-half of the emitted wavelength. That’s why the correct choice is 1/2. Using a thickness of a full wavelength would not produce the fundamental resonance, and a quarter-wavelength thickness relates to other modes or matching-layer effects rather than the basic thickness-mode resonance.

In thickness-mode transducers, resonance occurs when the crystal thickness corresponds to half the acoustic wavelength inside the crystal. The emitted wavelength is λ = v/f, with v the speed of sound in the crystal and f the drive frequency. For fundamental resonance, the crystal thickness d satisfies d = λ/2, so the thickness is about one-half of the emitted wavelength. That’s why the correct choice is 1/2. Using a thickness of a full wavelength would not produce the fundamental resonance, and a quarter-wavelength thickness relates to other modes or matching-layer effects rather than the basic thickness-mode resonance.