Which term describes the gradual spread of the ultrasound beam in the far field?

Which term describes the gradual spread of the ultrasound beam in the far field?

• A. Beam divergence
• B. Attenuation
• C. Focal depth
• D. Axial resolution

Answer: (A)

Beam divergence describes how the ultrasound beam gradually spreads as it travels into the tissue, especially in the far field. This spreading happens because a finite transducer aperture causes diffraction, so the beam widens with depth and lateral resolution can decrease as you look deeper. Attenuation means energy loss with depth, focal depth is where the beam is most focused, and axial resolution is about distinguishing structures along the beam; none of these describe the gradual beam spreading the way divergence does.

Beam divergence describes how the ultrasound beam gradually spreads as it travels into the tissue, especially in the far field. This spreading happens because a finite transducer aperture causes diffraction, so the beam widens with depth and lateral resolution can decrease as you look deeper. Attenuation means energy loss with depth, focal depth is where the beam is most focused, and axial resolution is about distinguishing structures along the beam; none of these describe the gradual beam spreading the way divergence does.