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  • A lamp emits monochromatic green light uniformly in all directions. The lamp is efficient in converting electrica

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 \mathrm{~W} of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of 10 \mathrm{~m} from the lamp will be:
 

Option: 1

1.34 \mathrm{~V} / \mathrm{m}

 


Option: 2

2.68 \mathrm{~V} / \mathrm{m}
 


Option: 3

5.36 \mathrm{~V} / \mathrm{m}
 


Option: 4

9.37 \mathrm{~V} / \mathrm{m}


Answers (1)

best_answer

\mathrm{S_{a v}=\frac{P}{4 \pi R^2}=\frac{1}{2} \varepsilon_0 \mathrm{cE}_0^2}

\mathrm{\therefore \mathrm{E}_0 \sqrt{\frac{\mathrm{P}}{2 \pi \mathrm{R}^2 \varepsilon_0 \mathrm{C}}} }

\mathrm{=\sqrt{\frac{3}{2 \times 3.14 \times 100 \times 8.85 \times 10^{-12} \times 3 \times 10^8}} }

\mathrm{=1.34 \mathrm{~V} / \mathrm{m}}

Hence option 1 is correct.




 

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