A transducer operating at which frequency would have the thickest element(s)?

The frequency of a transducer is inversely related to the thickness of its piezoelectric element. Lower frequency transducers require thicker elements to efficiently convert electrical signals into acoustic waves and vice versa. In diagnostic ultrasound, transducers operating at lower frequencies, such as 1 MHz and 2 MHz, utilize thicker elements to produce the longer wavelengths associated with these frequencies.

At 2 MHz, the element is thicker compared to those used for higher frequencies, such as 5 MHz and 10 MHz, where the shorter wavelengths necessitate thinner elements. As a result, the correct choice is 2 MHz, as it represents a frequency low enough to require a relatively thick piezoelectric element, thus enhancing the transducer's ability to generate lower frequency sound waves effectively.