Calculate the electric and magnetic fields produced by the radiation coming form a `30piW` bulb at a distance of `3m`. Assume that the efficiency of the bulb is `10%` and it is a point source.

Explanation

Intensity at distance `r` form a point source
`I = (P)/(4pir^(2))`
Efficiency `eta = ("output")/("input") = (P)/(P')`
`P = etaP' = ((10)/(100))(30pi) = 3piW`
`I = (P)/(4pir^(2)) = (3pi)/(4pi(3)^(2)) = (1)/(12)(W)/(m^(2))`
`= (1)/(2)in_(0)E_(0)^(2)c`
`(1)/(12) = (1)/(2)in_(0)E_(0)^(2) xx 3 xx 10^(8)`
`E_(0)^(2) = (10^(-8))/(18in_(0)) = (10^(-8))/(18xx8.85xx10^(-12)) = (10^(4))/(18xx8.85)`
`E_(0) = (100)/(sqrt(18xx8.85)) = 2.66V//m`
`B_(0) = (E_(0))/(c) = (2.66)/(3xx10^(8)) = 0.88xx10^(-8) T`