ARDMS Ultrasound Physics & Instrumentation Practice Exam

What phenomenon describes the spread of a sound beam as it travels through a medium?

1. Reflection

2. Refraction

3. Divergence

4. Attenuation

The correct answer is: Divergence

The phenomenon that describes the spread of a sound beam as it travels through a medium is known as divergence. As sound waves propagate from the transducer, they begin to fan out or spread, resulting in a larger area being covered by the sound wave as distance increases from its source. This divergence is influenced by factors such as the beam width and the frequency of the sound. In ultrasound imaging, understanding divergence is important because it affects resolution. As a beam diverges, the focus may become less defined, potentially impacting the ability to discern details in the ultrasound image. Higher frequency sound waves tend to have less divergence, allowing for better spatial resolution as they travel through the body than lower frequency waves. Reflection refers to the bouncing back of sound waves when they encounter a boundary between different media, while refraction involves the bending of waves as they pass from one medium into another, changing speed due to differences in density. Attenuation is the reduction in the strength of the sound wave as it travels through a medium, primarily due to absorption, scattering, and reflection, rather than the geometric spreading of the beam itself.