Find the minimum thickness of the ceramic needed for a transducer that will resonate at a frequency of 1.5 MHz. A transducer can also be used in reverse to detect sound. As sound waves compress and expand the transducer material, the transducer outputs an electrical signal that is an analogue likeness of the pressure wave that caused it. The bigger the difference the more reflection there is. Using transducers for transmitters and detectors together, pulses or continous waves can be sent out through materials and the reflections analysed to give information about the depth and types of layers in the material.
Scans can test for ovarian cancer and defects in foetuses.
The speed and impedance for some biological tissues are shown in the table. The wavelengths are about 1mm to 2mm. The different acoustic impedances of the various organs means there will be reflections of varying strengths at the internal boundaries between the organs. Also, the reflected pulses will return at different time intervals, or continuous waves will return with phase differences. At higher powers, ultrasound can be used in therapy because it deposits heat in the deeper muscles, bones and joints.