Question

A lamp emits monochromatic green light uniformly in all directions. The lamp is `3%` efficient in converting electrical power to electromagnetic waves and consumes `100 W` of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of `5` m from the lamp will be:
A. `1.34 V//m`
B. `2.68 V//m`
C. `4.02 V//m`
D. `5.36 V//m`

Answer 1

Correct Answer - b
Mean Intensity `=(P)/(4pir^(2))=(1)/(2)in_(0)E^(2)xxC`
`:.E=sqrt((P)/(2pir^(2)in_(0)C))=2.68 Vm_(-1)`