If the bulk modulus of a medium increases while density remains constant, what happens to the speed of ultrasound?

If the bulk modulus of a medium increases while density remains constant, what happens to the speed of ultrasound?

• A. It remains the same
• B. It becomes invalid
• C. It increases
• D. It decreases

Answer: (C)

Ultrasound travels faster when a medium is stiffer relative to its inertia. The speed of a compressional wave is tied to how resistant the material is to compression (bulk modulus) compared with its density. If density stays constant and the bulk modulus increases, the ratio B/ρ grows, so the speed increases. Intuitively, a stiffer medium transmits the pressure disturbance more quickly because it resists compression more strongly. Therefore, the speed goes up.

Ultrasound travels faster when a medium is stiffer relative to its inertia. The speed of a compressional wave is tied to how resistant the material is to compression (bulk modulus) compared with its density. If density stays constant and the bulk modulus increases, the ratio B/ρ grows, so the speed increases. Intuitively, a stiffer medium transmits the pressure disturbance more quickly because it resists compression more strongly. Therefore, the speed goes up.