Radio waves and microwaves are used in therapy to provide \"deep heating\" of ti
ID: 1451334 • Letter: R
Question
Radio waves and microwaves are used in therapy to provide "deep heating" of tissue because the waves penetrate beneath the surface of the body and deposit energy. We define the penetration depth as the depth at which the wave intensity has decreased to 37% of its value at the surface. The penetration depth is 15 cm for 27 MHz radio waves. For radio frequencies such as this, the penetration depth is proportional to , the square root of the wavelength.
For 27 MHz radio waves, the wave intensity has been reduced by a factor of 3 at a depth of approximately 15 cm. At this point in the tissue, the electric field amplitude has decreased by a factor of:
a) 3. b) 3. c) 33. d) 9.Explanation / Answer
The intensity of a wave is proportional to its amplitude squared.
Therefore if the inensity is reduced by a factor of 3 then the amplitude will be decreased by a factor of sqrt(3).
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