In ultrasound, the speed of sound is primarily affected by which two properties of the medium?

The speed of sound in a medium is fundamentally determined by its density and elasticity. Elasticity refers to the ability of a material to return to its original shape after being deformed, which greatly influences how sound waves propagate through that medium. Higher elasticity typically allows sound waves to travel faster.

Density also plays a crucial role; while sound travels faster in less dense materials (like gases), it moves more slowly in denser media (like liquids and solids, where the molecular structure is more tightly packed). The opposing influences of density and elasticity result in a complex relationship that dictates sound speed.

Thickness, mentioned in one of the choices, does not directly influence the speed of sound; rather, it can affect the amplitude and intensity of the waves, but not the inherent speed of propagation. Other factors like temperature and pressure can influence sound speed, but density and elasticity are the primary properties that fundamentally dictate the speed of sound in different media.