What happens to divergence in the far field when wavelength is decreased?

Divergence refers to the spreading out of the ultrasound beam as it travels away from the transducer, particularly in the far field. The relationship between wavelength and divergence is significant in understanding how ultrasound waves behave.

When the wavelength of the ultrasound wave is decreased, the beam becomes narrower as it propagates. This is because a smaller wavelength allows for a more focused beam, resulting in less spreading or divergence in the far field. The phenomenon can be understood through the equations governing beam width and resolution; as wavelength decreases, the ability of the system to maintain beam focus improves, reducing divergence.

In practical terms, this means that when using higher frequency transducers (which have a shorter wavelength), the ultrasound beam will diverge less compared to when lower frequency transducers are used. Therefore, a decrease in wavelength leads to decreased divergence, allowing for better imaging resolution and clearer delineation of structures in the ultrasound field.