Which frequency value matches a 22-meter wavelength used in short-wave diathermy?

• A. 27.12 MHz
• B. 40 MHz
• C. 13.56 MHz
• D. None of the above

Answer: (C)

The essential idea is the inverse relationship between wavelength and frequency for electromagnetic waves. The frequency f relates to wavelength λ by f = c/λ, where c is about 3 × 10^8 meters per second. If the wavelength is 22 meters, the corresponding frequency is roughly 3 × 10^8 divided by 22, which is about 13.6 MHz. In short-wave diathermy, standard operating bands include 13.56 MHz, 27.12 MHz, and 40 MHz. The 13.56 MHz band is the closest standard frequency to 13.6 MHz, aligning with a 22-meter wavelength. The other options correspond to shorter wavelengths (about 11 meters for 27.12 MHz and about 7.5 meters for 40 MHz), so they do not match a 22-meter wavelength.