The average output power of a GSM cellular phone is 1.0W when it is \"ON\". The

Question

The average output power of a GSM cellular phone is 1.0W when it is "ON". The phone can be treated as a point source of E-M waves emitting spherical waves. (a) Calculate the intensity and peak electric field Emax of the phone's E-M waves in your brain, which is about 5.0 cm away from the phone when it is applied directly against your ear; (b) What is the intensity and peak electric field of E-M wave inside a microwave oven, whose area of cross-section is A=0.25mx0.30m and the average E-M wave power is 500-W. (c) How the electric field in (a) compares with the safety regulation of EPA for microwave oven, which says that leaking of more than 5% of the E-field from the oven is harmful to human body.

Explanation / Answer

apply the formula Intensity I = power/area = Emax^2 /2uoC

Where E is Electric field and uo is 4pi e-7

C is speed of light

A is area A = 4pi r^2

so

part A:

I = 1/(4*3.14 * 0.05 *0.05)

I = 31.84 W/m^2

----------------------

again I = Power/area

here A = area = 0.25* 0.3 m^2

so

I = 50/(0.25* 0.3)

I = 666.67 W/m^2

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