What statement is true about the period of a diagnostic ultrasound wave?

What statement is true about the period of a diagnostic ultrasound wave?

• A. It is determined by the sound source only
• B. It can be adjusted by changing the medium
• C. It varies with depth
• D. It is never adjustable

Answer: (A)

Period is the time for one complete cycle, and it is the reciprocal of the frequency (T = 1/f). In diagnostic ultrasound, the frequency is set by the transducer and its drive electronics, so the timing of each cycle is determined by the sound source. The medium affects how fast the wave travels (speed c) and thus the wavelength via λ = c/f, but it does not change the period for a given source frequency. Depth or changing the medium won’t alter the period unless you change the source frequency. So the period being set by the sound source best explains why it remains fixed for a given transducer.

Period is the time for one complete cycle, and it is the reciprocal of the frequency (T = 1/f). In diagnostic ultrasound, the frequency is set by the transducer and its drive electronics, so the timing of each cycle is determined by the sound source. The medium affects how fast the wave travels (speed c) and thus the wavelength via λ = c/f, but it does not change the period for a given source frequency. Depth or changing the medium won’t alter the period unless you change the source frequency. So the period being set by the sound source best explains why it remains fixed for a given transducer.