Manitude of the electric and magnetic field in an electromagnetic wave radiated by a `200 W` bulb at a distance 2m from it is assuming efficiency of bulb is `5%` and it behaves like a point source.

Explanation

Effective power of the bulb `P=(5)/(100)xx200=10` watt
Intensity at distance r is given by
`l=(P)/(4pi r^(2))`
`=(10)/(4xx3.14xx2^(2))("watt")/(m^(2))`
`=(10)/(16.xx3.14)("watt")/(m^(2))`
`=0.199("watt")/(m^(2))`
`=0.2("watt")/(m^(2))`
`l=(1)/(2)epsi_(0)E_(0)^(2)c`
`E_(0)^(2)=(2l)/(cxxepsi_(0))`
`E_(0)sqrt((2l)/(3xx10^(8)xx8.85xx10^(-12)))`
`E_(0)=112.27(N)/(C)`
`B_(0)=(E_(0))/(C)=(12.27)/(3xx10^(8))=(12.27)/(3)xx10^(-8)T`
`=4.09xx10^(8)T`