Final answer:
The power threshold needed to produce thermal effects with shortwave diathermy is not specified directly in the given options. However, it is known that intensities of 10³ to 10⁴ W/m² are used for similar forms of deep-heat treatments in medical applications, which may provide a reference for what might be expected for diathermy. We lack the specific context to accurately determine the necessary power threshold from the provided choices.
Step-by-step explanation:
The question is asking about the power threshold required to produce thermal effects with shortwave diathermy, a form of medical treatment that uses electromagnetic energy to generate heat within body tissues, aiding in healing and pain reduction. While the given options do not directly provide a clear answer, based on additional information related to medical applications of diathermy, we can deduce the correct power threshold.
High-intensity ultrasound in tissue, which is similar in concept to shortwave diathermy, commonly uses intensities of 10³ to 10⁴ W/m² for deep-heat treatments. Considering that shortwave diathermy also induces thermal effects within tissue, one could infer that the power threshold should be comparable to these intensities. However, none of the given answers (10 W, 12 W, 24 W, 48 W) directly correspond to these values.
Therefore, we would need either more information to make a direct comparison or look at other resources to determine the typical power output of a shortwave diathermy device. Without additional context or information, we cannot accurately select the correct answer from the provided choices.