In which scenario is absorption most likely to occur?

Absorption of ultrasound energy in tissues is closely linked to the frequency of the sound waves. When higher frequency sound waves are utilized, they are absorbed more readily by the tissues they penetrate. This is due to the interactions at the molecular level, where more frequent oscillations of higher frequency waves create greater friction and convert sound energy into heat. This results in increased attenuation as the sound travels through the medium.

In contrast, lower frequency sound waves penetrate deeper but experience less absorption. While absorption occurs regardless of frequency, it is significantly more pronounced at higher frequencies. Thus, scenarios involving high-frequency sound are most conducive to absorption effects in tissues, making this option the most accurate in indicating when absorption is likely to occur.