Which zone is closest to the transducer?

Which zone is closest to the transducer?

• A. Doppler zone
• B. Fresnel zone
• C. Far field
• D. Near zone

Answer: (D)

The main idea is the distinction between the near field and the far field of an ultrasound transducer. Right after the transducer emits a pulse, the beam is still converging and patterns are complex; this region is the near field. It’s also known as the Fresnel zone, and it extends from the transducer face up to the point where the beam starts to become more stable and diverge—this boundary marks the start of the far field (Fraunhofer zone). The near field is the region closest to the transducer, so that’s why it’s the correct choice. For context, the near-field length depends on transducer diameter and wavelength (approximately N ≈ D²/(4λ) for a circular aperture). The Doppler term isn’t a standard zone designation here, so it isn’t the region closest to the transducer.

The main idea is the distinction between the near field and the far field of an ultrasound transducer. Right after the transducer emits a pulse, the beam is still converging and patterns are complex; this region is the near field. It’s also known as the Fresnel zone, and it extends from the transducer face up to the point where the beam starts to become more stable and diverge—this boundary marks the start of the far field (Fraunhofer zone). The near field is the region closest to the transducer, so that’s why it’s the correct choice. For context, the near-field length depends on transducer diameter and wavelength (approximately N ≈ D²/(4λ) for a circular aperture). The Doppler term isn’t a standard zone designation here, so it isn’t the region closest to the transducer.