Which of the following are true about acoustic impedance? a. It is me

1.	Which of the following are true about acoustic impedance? a. It is measured in kg m-2 b. The acoustic impedance of fat is lower than most other tissues c. The acoustic impedance of air is almost zero d. It is independent of temperature e. The intensity of ultrasound is directly proportional to the acoustic impedance and to the wave amplitude
Answer» a. False. The acoustic impedance is a product of ultrasound velocity (in m s^-1 ) and density of the medium (in kg m^-3 ). Therefore, its unit is kg m^-2 s ^-1 , which is also termed rayl after Lord Rayleigh. b. True. The lower velocity of ultrasound in fat combined with fat being of lower density leads to a lower acoustic impedance. c. True. This is mainly due to its low density. d. False. It changes with temperature as the material density and stiffness may change. e. False. It is proportional to the acoustic impedance and to the square of the amplitude.

Which of the following are true about acoustic impedance? a. It is measured in kg m-2 b. The acoustic impedance of fat is lower than most other tissues c. The acoustic impedance of air is almost zero d. It is independent of temperature e. The intensity of ultrasound is directly proportional to the acoustic impedance and to the wave amplitude

Answer»

a. False. The acoustic impedance is a product of ultrasound velocity (in m s^-1 ) and density of the medium (in kg m^-3 ). Therefore, its unit is kg m^-2 s ^-1 , which is also termed rayl after Lord Rayleigh.

b. True. The lower velocity of ultrasound in fat combined with fat being of lower density leads to a lower acoustic impedance.

c. True. This is mainly due to its low density.

d. False. It changes with temperature as the material density and stiffness may change.

e. False. It is proportional to the acoustic impedance and to the square of the amplitude.

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