ARDMS Ultrasound Physics & Instrumentation Practice Exam

Which factor does NOT affect the speed of sound in a medium?

1. Temperature

2. Density of the medium

3. Color of the medium

4. Stiffness of the medium

The correct answer is: Color of the medium

The speed of sound in a medium is influenced by several physical properties, but the color of the medium does not play a role in this phenomenon. Sound travels through physical media—such as solids, liquids, and gases—based on their density, temperature, and stiffness. Temperature affects the speed of sound because as the temperature of a medium increases, its molecules move faster, which facilitates quicker transmission of sound waves. The density of the medium also impacts how sound travels; typically, in gases, sound travels faster in denser media, while in solids, stiffness often has a more significant impact than density alone. Stiffness, or the ability of a medium to resist deformation, directly affects sound speed because sound waves propagate more quickly through stiffer materials due to the efficient transmission of kinetic energy. In summary, while temperature, density, and stiffness significantly influence the speed of sound, the color of the medium is an optical property and does not affect how sound waves propagate through that medium. Therefore, the option indicating the color of the medium as a non-factor is accurate.