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A lamp emits monochromatic green light u...

A lamp emits monochromatic green light uniformly in all direction. The lamp is 5% effiecient in converting electrical power to electromagnetic waves and cosumes 100W of power. What is the amplitude of electric field associated with the electromagnetic radiation at a distance of 4m from the lamp?

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Power converted into e.m. wave, `P=5/100xx100=5W`
Average intensity of e.m. wave is, `I=P/(4pir^2)=1/2 in_0E_0^2c`
or `E_0=sqrt(P/(2pir^2in_0c))=[5/(2xx(22//7)xx(8/85xx10^-12)xx(3xx10^8))]^(1//2)=4.33Vm^-1`
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