Final answer:
The reflection of the incident ultrasound beam varies primarily with acoustic impedance and the incident angle. Acoustic impedance dictates how much energy is reflected at the boundary between media, and the incident angle affects the reflection based on Snell's law.
Step-by-step explanation:
The amount of reflection of the incident ultrasound beam varies with acoustic impedance and incident angle. Acoustic impedance is a property of a medium that affects how much of the ultrasound wave is reflected at the boundary between two different media. When ultrasound waves encounter a boundary with a differing acoustic impedance, some of the wave energy is reflected back while some is transmitted.
The incident angle also plays a crucial role in reflection; when an ultrasound wave hits a boundary at a non-perpendicular angle (i.e., not 90 degrees), the reflection and transmission of the wave are governed by Snell's law, and the amount of reflected energy can vary with the angle of incidence.