Two near zone lengths are equal to what dimension of the transducer?

Two near zone lengths are equal to what dimension of the transducer?

• A. Transducer Diameter
• B. Beam Width
• C. Wavelength
• D. Focal Length

Answer: (A)

The near field (Fresnel zone) length is governed by the transducer’s aperture size. For a circular aperture, the near field length NZL is proportional to the square of the diameter and inversely proportional to the wavelength (NZL ≈ D^2/(4λ)). This shows that the transducer diameter is the dimension that sets how far the near field extends. The other options describe beam characteristics or properties not determined by the transducer’s physical size in the same way: beam width is about the beam itself, wavelength is a medium/frequency property, and focal length is a separate design parameter. Therefore, two near zone lengths relate to the transducer’s diameter.

The near field (Fresnel zone) length is governed by the transducer’s aperture size. For a circular aperture, the near field length NZL is proportional to the square of the diameter and inversely proportional to the wavelength (NZL ≈ D^2/(4λ)). This shows that the transducer diameter is the dimension that sets how far the near field extends. The other options describe beam characteristics or properties not determined by the transducer’s physical size in the same way: beam width is about the beam itself, wavelength is a medium/frequency property, and focal length is a separate design parameter. Therefore, two near zone lengths relate to the transducer’s diameter.