ARDMS Ultrasound Physics & Instrumentation Practice Exam

What physical property describes the stiffness of a medium?

1. Inertia

2. Elasticity

3. Viscosity

4. Density

The correct answer is: Elasticity

The correct answer is elasticity, which is a critical physical property that defines the stiffness of a medium. Elasticity refers to the ability of a material to return to its original shape after being deformed by an applied force. In the context of ultrasound, a medium with higher elasticity will transmit sound waves more efficiently because the material can quickly return to its undisturbed state, allowing sound energy to propagate. When considering this property, it's important to recognize that different materials exhibit varying levels of stiffness, which is essential in determining the speed of sound within those materials. A stiffer medium typically allows sound to travel faster, as the particles can transmit energy across the medium more effectively. While inertia, viscosity, and density are also important physical properties of materials, they do not specifically define stiffness. Inertia relates to an object's resistance to changes in motion, viscosity refers to a fluid's resistance to flow, and density is the mass per unit volume of a substance. None of these attributes directly address the medium's ability to resist deformation and return to its original state, which is why elasticity is the appropriate answer in this context.