1) A diathermy machine, used in physiotherapy, generates electromagnetic radiati

Question

1) A diathermy machine, used in physiotherapy, generates electromagnetic radiation that gives the effect of "deep heat" when absorbed in tissue. One assigned frequency for diathermy is 13.56 MHz. What is the wavelength of this radiation?

2) Two electrical oscillators are used in a heterodyne metal detector to detect buried metal objects. The detector uses two identical electrical oscillators in the form of LC circuits having resonant frequencies of 790 kHz. When the signals from the two oscillating circuits are combined, the beat frequency is zero because each has the same resonant frequency. However, when the coil of one circuit encounters a buried metal object, the inductance of this circuit increases by 1.250%, while that of the second is unchanged. Determine the beat frequency that would be detected in this situation.

Explanation / Answer

1) frequency for diathermy = 13.56 MHz

wavelength = c / f

= 3 * 108 / 13.56 * 106

= 22.12 m

wavelength = 22.12 m

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