ARDMS Sonography Principles and Instrumentation (SPI) Practice Exam 2026 - Free Sonography Exam Questions and Study Guide

The transmission angle will be greater than the incident angle when the second medium is more dense than the first medium. This phenomenon can be explained using Snell's Law, which describes how the angle of incidence and the angle of refraction (or transmission) relate to the speeds of sound in the two media.

In this case, when the denser medium (medium 2) has a higher sound speed than the less dense medium (medium 1), the transmission angle becomes greater than the incident angle. This occurs because higher density usually corresponds with lower sound speed, yet when transitioning to a medium where sound speed increases (even if it is more dense), the angle of transmission increases.

Understanding that the wave travels faster in medium 2 leads to the conclusion that the transmission angle will exceed the incident angle. This principle is critical in envisioning how ultrasound behaves at boundaries between different tissues, impacting how images are formed during sonography.