Physicians use a high-frequency (f = 1-5 MHz) sound waves,called ultrasound, to image internal organs. The speed ofthese ultrasound waves is 1480 m/s in muscle and 344 m/s inair. At what angle from the normal does an ultrasound beamenter the heart wall if it leaves the lungs at an angle of 9.73degrees from the normal to the heart wall? Assume the speedof sound in the lungs is 344 m/s. What is the critical agle for sound waves in air incident on muscle?