Which phenomenon occurs when ultrasonic energy is converted into another form of energy such as heat?

• A. Reflection
• B. Scattering
• C. Refraction
• D. Absorption

Answer: (D)

Absorption is the process by which ultrasonic energy is taken up by the medium and converted into heat through molecular interactions and friction. As the wave propagates, part of its energy is dissipated as heat, contributing to attenuation and a tiny temperature rise in tissues. This conversion to heat is what makes absorption the primary mechanism of energy loss in tissue. By contrast, reflection sends energy back toward the transducer at interfaces, scattering redirects energy in many directions, and refraction bends the beam when it enters a medium with a different sound speed. So, when the question points to energy becoming heat, absorption is the best explanation.