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 `10 m` from the lamp will be

Options

A. 1.34 V/m
B. 2.68 V/m
C. 5.36 V/m
D. 9.37 V/m

Answer

D

Explanation

`S_(av) = (P)/(4 pi R^(2)) = (1)/(2) epsilon_(0) c E_(0)^(2) " " therefore E_(0) = sqrt((P)/(2 pi R^(2) epsilon_(0)c))`
`= sqrt( (3)/(2 xx 3.14 xx 100 xx 8.85 xx 10^(-12) xx 3 xx 10^(8))) = 1.34` V/m