ARDMS Ultrasound Physics & Instrumentation Practice Exam 2026 – Complete Study Resource

When sound waves travel through a medium with high density, their speed decreases due to the increased resistance and inertia of the denser molecules. Sound travels fastest in gases at lower densities but as the density increases (typically when transitioning from gas to liquid or solid), the particles are packed more closely together, which can increase the medium's stiffness but also inhibit the speed of molecular vibrations due to the increased mass. This results in a slower wave speed.

As a consequence of the reduced speed, the wavelength will become shorter. Wavelength is inversely proportional to wave speed in a given frequency; when the wave speed decreases while the frequency remains constant, the wavelength must also decrease. Therefore, the correct answer indicates that as sound travels through a denser medium, the wave's speed decreases, and its wavelength becomes shorter.