Final answer:
The ultrasound frequency range used for therapeutic purposes is 1-3 MHz, which is option b. This range is particularly effective for deep-heat treatments in physical therapy and sports medicine.
Step-by-step explanation:
In the context of therapeutic ultrasound applications, the frequency range that is most commonly used is 1-3 MHz. This frequency range is effective for deep-heat treatments known as ultrasound diathermy, which is utilized in physical therapy and sports medicine. Ultrasound diathermy helps in treating injured or overworked muscles by relieving pain and improving flexibility. Frequencies of 0.8 to 1 MHz are typical for deep heating purposes, and it requires the skill of the therapist to prevent tissue damage, including "bone burns," owing to overheating and cavitation effects. Therefore, the correct answer to which ultrasound frequency range is used for therapeutic purposes is option b: 1-3 MHz.