An ultrasonic transmitter is in the form of a piezoelectric disc of diameter 2.5 cm and thickness 1.0 cm. The front face of the disc is placed directly onto biological tissue; the rear face is in contact with air. A pulse launched from the centre of the disc divides into two equal pulses, each of power 1 W and width 0.5 µs, one travelling towards the front face and one towards the rear face.
(a) Use the data given below to derive the form of the signal entering the tissue.
(b) Explain in detail what modifications should be made to the transducer so that the signal entering the tissue is a close approximation to a single pulse.