The peak value of electric field produced by the radiation coming from a 100 watt bulb at a distance of 3m is ( assume that the efficiency of the bulb is 2.5% and it is a point source)

Useful intensity,  I=powerarea=100×2.51004π(3)2 ⇒I=2.536πWm−2Half of this intensity(I) belongs to electric field and half of that to magnetic field  I2=14∈0E02C ⇒E0=2I∈0C ⇒E0=2×(2.5/36π)(14π×9×109)×(3×108)=4.08Vm−1