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 $$5m$$ from the lamp will be nearly.

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 $$5m$$     from  the lamp will be nearly.

Infinity Learn · Accepted Answer

Wavelength  of monochromatic green $$light=5.5$$×$$10$$−$$5cm$$       $$IntensityI=PowerArea=100$$×(3100)4$$π$$(5)2=3100$$$$π$$Wm−$$2$$     Now,  half of this intensity $$(I)     belongs  to electric field and half of that to magnetic field, therefore, $$I2=14$$ε$$0E02C$$     or  $$E0=2I$$ε$$0C=2$$×(3100$$π$$)(14$$π×$$9$$×$$109)×$$(3$$×$$108)=625$$×$$30=7.2$$     ∴$$E0=2.68V/m$$

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