Unless otherwise indicated, for problems in this section, assume that the speed of sound through human tissues is 1540 m/s.
In the clinical use of ultrasound, transducers are always coupled to the skin by a thin layer of gel or oil, replacing the air that would otherwise exist between the transducer and the skin. (a) Using the values of acoustic impedance given in the table calculate the intensity reflection coefficient between transducer material and air. (b) Calculate the intensity reflection coefficient between transducer material and gel (assuming for this problem that its acoustic impedance is identical to that of water). (c) Based on the results of your calculations, explain why the gel is used.
OpenStax College Physics 2e, 17.7 Ultrasound, exercise 10