What are the two zones the sound beam enters after leaving the transducer?

What are the two zones the sound beam enters after leaving the transducer?

• A. Far zone and Fresnel zone
• B. Near zone and Far zone
• C. Near zone and Fresnel zone
• D. Fresnel zone and Far zone

Answer: (C)

The beam in ultrasound travels through two distance-based regions: the near field (also called the Fresnel zone) and the far field (also called the Fraunhofer zone). Right after it leaves the transducer, the beam is in the near field, which is the region where the wave fronts are still developing and the pattern can be quite complex. The term Fresnel zone is simply another name for this same initial region. As the beam continues, it then enters the far field beyond that boundary. So the option pairs the near zone with the Fresnel zone because those two terms describe the same portion of the beam’s path right after emission. The far zone (Fraunhofer) would come after, not immediately after leaving.

The beam in ultrasound travels through two distance-based regions: the near field (also called the Fresnel zone) and the far field (also called the Fraunhofer zone). Right after it leaves the transducer, the beam is in the near field, which is the region where the wave fronts are still developing and the pattern can be quite complex. The term Fresnel zone is simply another name for this same initial region. As the beam continues, it then enters the far field beyond that boundary.

So the option pairs the near zone with the Fresnel zone because those two terms describe the same portion of the beam’s path right after emission. The far zone (Fraunhofer) would come after, not immediately after leaving.