The U.S. Food and Drug Administration limits the radiation leakage of microwave

Question

The U.S. Food and Drug Administration limits the radiation leakage of microwave ovens to no more than 5.0 mW/cm2 at a distance of 2.00 in. A typical cell phone, which also transmits microwaves, has a peak output power of about 2.0 W.
(a) Approximating the cell phone as a point source, calculate the radiation intensity of a cell phone at a distance of 2.00 in.
_____________ mW/cm2

How does the answer compare with the maximum allowable microwave oven leakage? (Enter the ratio of cellphone intensity to microwave intensity.)
I cell phone/I microwave
= __________________

(b) The distance from your ear to your brain is about 2 in. What would the radiation intensity in your brain be if you used a Bluetooth headset, keeping the phone in your pocket, 1.0 m away from your brain? Most headsets are so-called Class 2 devices with a maximum output power of 2.5 mW. (Include both the radiation from the phone and the headset.)
_________________ mW/cm2

Explanation / Answer

(a) Radiation intensity (Icell) of the cellphone power iscalculated as                   Icell = P / A                          = P / (4r2)                          = 2.0 W/ 4(0.0508 m)^2                          = 61.7 W/ m2                          = 61.7*10-4 W/cm2                          = 6.17 mW/cm2 The ratio of cellphone power / microwave power                          = (6.17mW/cm2) / (5.0 mW/cm2)                          = 1.233 b) The between the pocket to the brain = 1.0m Then radiation intensity in your brain is                         I = P /4r2                           = (2.5mW) / [4(1.0m)2]                           = 0.2 mW (a) Radiation intensity (Icell) of the cellphone power iscalculated as                   Icell = P / A                          = P / (4r2)                          = 2.0 W/ 4(0.0508 m)^2                          = 61.7 W/ m2                          = 61.7*10-4 W/cm2                          = 6.17 mW/cm2 The ratio of cellphone power / microwave power                          = (6.17mW/cm2) / (5.0 mW/cm2)                          = 1.233 b) The between the pocket to the brain = 1.0m Then radiation intensity in your brain is                         I = P /4r2                           = (2.5mW) / [4(1.0m)2]                           = 0.2 mW

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