Calculate the electric and magnetic fields produced by the radiation coming from a `100` W bulb at a distance of `3 m`. Assume that the efficiency of the bulb is `25%` and it is a point source.

Explanation

Intensity at a distance `r` from a point source of power `P` is given by
`I=P/((4pir^2)`
So, intensity at a distance of `3 m` from the bulb with `2.5%` efficiency will be
`I = 100/(4pi(3)^2)xx2.5/100`
`0.022 W//m^2`
Half of the intensity is provided by eletric field and half by magnetic field
`I_E=1/2=0.011 W//m^2`
but, `I_E` (is given by) `1/2 epsilon_0 E^2c`
`I_E = 1/2 epsilon_0 E^2 c` or `E=sqrt((2I_E)/(epsilon
_0 c)`
Substituting the values,we have
`E=sqrt(2xx0.011)/((8.85xx10^-12)(3xx10^8))`
`2.9 V//m`.