What determines the acoustic impedance of a material and why is it useful in understanding ultrasound imaging?
Acoustic impedance is the density of a material multiplied by the speed of sound in the material.
Knowing these two values allows use to calculate how much of the sound energy is reflected at an interface between two materials, or two different types of tissue in the body. The greater the difference, the more reflection. This is the reason for the use of coupling gel between the scanner probe and the skin, removing trapped air, to reduce reflection of ultrasound at the skin, by reducing the acoustic impedance difference.
DA
Related Physics A Level answers
All answers ▸By considering Newton's second law and his law of gravitation, derive an expression for gravitational field strength g in terms of its mass, m, the distance from its center of mass, r, and the gravitational constant, G.
How, given the threshold frequency and the kinectic enery of a photon, do you determine the frequency of the phton?
Why is the classical model of light insufficient in explaining the photoelectric effect?
An ideal gas at a temperature of 22 C is trapped in a metal cylinder of volume 0.2 m^3 at a pressure of 1.6x10^6 Pa. The gas has a molar mass of 4.3 x 10^(-2) kg mol^(-1). Calculate the density of the gas in the cylinder.