A lamp emits monochromatic green light uniformly in all directions. The lamp is 3% efficient in converting electrical power to electromagnetic waves and consumes 100W of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of 10m from the lamp will be:

1.34 V/m      

$S_{av} = \frac{P}{4\pi R^2} = \frac{1}{2} \epsilon_0 c E_0^2 = 1.34V/m$