Density is defined as what?

Density is defined as what?

• A. Ratio of speed to frequency
• B. Material color
• C. Concentration of mass within a volume
• D. Wavelength

Answer: (C)

Density measures how much mass is packed into a given volume. It’s defined as mass per unit volume (ρ = m/V). In ultrasound, density, together with stiffness, determines how fast sound travels and the acoustic impedance Z = ρ c that the wave meets when moving between materials. The ratio of speed to frequency gives wavelength, not density; material color is unrelated; and wavelength itself is speed divided by frequency.

Density measures how much mass is packed into a given volume. It’s defined as mass per unit volume (ρ = m/V). In ultrasound, density, together with stiffness, determines how fast sound travels and the acoustic impedance Z = ρ c that the wave meets when moving between materials. The ratio of speed to frequency gives wavelength, not density; material color is unrelated; and wavelength itself is speed divided by frequency.