Final answer:
While assuming continuous wave (cw) ultrasound, the duty factor
(DF) is "a. 0.2%".
Step-by-step explanation:
The duty factor (DF) for continuous wave (CW) ultrasound is typically expressed as a percentage, and in this case, it is "0.2%". The duty factor represents the proportion of time during which ultrasound is actually being emitted. For continuous wave ultrasound, the sound waves are transmitted continuously without interruption, resulting in a duty factor less than 1%.
In mathematical terms, the duty factor is calculated as the pulse duration divided by the pulse repetition period. For continuous wave ultrasound, where there is no pulse repetition, the duty factor simplifies to the duration of the transmitted wave divided by the total time.
Therefore, the duty factor is calculated as the time the ultrasound is on (pulse duration) divided by the total time, expressed as a percentage.