Final answer:
The echo time difference for tissues at different depths is used to calculate the scanner's resolution, and the period of the ultrasound must be smaller than this time to resolve details. A higher frequency is thus required, which should be within the normal operational range for diagnostic ultrasounds. The power output of an ultrasound device is computed by multiplying its intensity by the area of the emitting head.
Step-by-step explanation:
For part (a), the difference in echo times for tissues located at depths of 3.50 cm and 3.60 cm beneath the surface can be calculated by considering the distance each ultrasound wave must travel (to and from the tissue). Assuming the speed of sound in soft tissue is approximately 1540 m/s, the echo time difference is a crucial factor for determining the minimum resolution the scanner is capable of. If greater discrimination is required to see smaller details, then smaller echo time differences must be discerned.
For part (b), the period T of the ultrasound wave must indeed be smaller than the minimum resolving time for the scanner to differentiate between the reflectors. Since the period is the inverse of the frequency, a higher frequency ultrasound wave would be necessary. To calculate the minimum frequency required, one must use the relationship between speed, frequency, and wavelength. Diagnostic ultrasounds typically operate in the range of roughly 2 to 15 MHz, and the calculated frequency must be compared to this range to determine if it is normal.
The power output of an ultrasound device producing an intensity of 1.50×10² W/m² from a head measuring 3.00 cm by 5.00 cm can be calculated by multiplying the intensity by the area of the head.