Final answer:
The true average intensity of the ultrasound treatment with a spatial average intensity of 2.0 W/cm² and a duty cycle of 50% is 1.0 W/cm², corresponding to option (c).
Step-by-step explanation:
The true average intensity (also known as the temporal average intensity) of an ultrasound treatment based on a spatial average intensity (SAI) of 2.0 W/cm² and a duty cycle of 50% can be calculated using the formula: True Average Intensity = SAI × Duty Cycle. Therefore, the correct calculation is 2.0 W/cm² × 0.50 (or 50%), yielding a true average intensity of 1.0 W/cm².
In terms of multiple-choice options, the correct answer to this question is (c) 1.0 W/cm². This is because the ultrasound unit operates half the time (50% duty cycle) and at full intensity the other half of the time, resulting in an average intensity that is half of the SAI.