3.1. Calculate the intensity transmission coefficient 7; for the following interfaces, assuming that the ultrasound beam is exactly perpendicular to the interface: muscle/kidney, air/muscle, and bone/muscle. Discuss briefly the implications of these values of T₁ for ultrasonic imaging. 3.2. Repeat the calculations in Exercise 3.1 with the angle of incidence of the ultra- sound beam now being 60°.