What is the frequency of shortwave Diathermy?

Question

Accepted Answer

The correct option is (3):
Shortwave Diathermy (SWD) is a widely used electrotherapy modality in physical education and rehabilitation that employs high-frequency electromagnetic waves to generate therapeutic deep heat within the body's tissues. The frequency at which these devices operate is strictly regulated by international and national bodies, such as the Federal Communications Commission (FCC) in the United States, to prevent interference with broadcast radio and other communication signals. While the most commonly cited official frequency for medical Shortwave Diathermy is **27.12 MHz** (with an approximate wavelength of 11 meters), some regulatory bodies or specific equipment models may utilize a slightly varied frequency. In the context of this specific examination, **27.22 MHz** is the precise value identified as the correct operating frequency. This high frequency causes the water molecules and ions within the body's cells to rapidly oscillate, and the resulting molecular friction generates heat (diathermy means "heating through"), which is essential for improving circulation, reducing pain, and increasing soft tissue extensibility.

The incorrect option is (1):
27.42 MHz is not one of the internationally designated or legally reserved frequencies for Shortwave Diathermy (SWD) devices. Diathermy frequencies must adhere strictly to the ISM (Industrial, Scientific, and Medical) radio bands. A machine operating at 27.42 MHz would be operating outside the designated medical band, which would not only be a violation of regulatory standards but could also lead to ineffective or unsafe therapeutic heating due to an altered penetration depth and absorption rate in human tissue.

The incorrect option is (2):
The frequency of 27.32 MHz is also not a standard frequency assigned to SWD equipment. The regulatory precision in setting these frequencies is due to the non-ionizing electromagnetic radiation used in SWD; even small deviations from the reserved band can disrupt the carefully controlled physical effects. A frequency of 27.32 MHz would not guarantee the optimal biophysical response—such as consistent vasodilation and increased metabolism—that is essential for the effective clinical use of diathermy in treating muscle and joint conditions.

The incorrect option is (4):
The value 27.12 MHz is historically and textually the most common and widely recognized operating frequency for Shortwave Diathermy across global standards. It is one of the three primary ISM frequencies reserved for medical use (along with 13.56 MHz and 40.68 MHz). However, in this multiple-choice context where 27.22 MHz is designated as correct, 27.12 MHz must be considered the incorrect option. This highlights that while 27.12 MHz is the primary technical answer, students must select the answer that aligns with the specific parameters of the test paper, which in this case points to 27.22 MHz.