The electric field of a plane electromagnetic wave varies with time of amplitude `2Vm^-1` propagating along z-axis. The average energy density of the magentic field is (in `Jm^-3`)

Options

A. `13.29xx10^(-12)`
B. `8.86xx10^(-12)`
C. `17.72xx10^(-12)`
D. `4.43xx10^(-12)`

Answer

B

Explanation

Amplitude of electric field and magnetic field are related by the relation Average energy density of the magnetic field is
`u_(B)=1/4(B_(0)^(2))/(mu_(0))=1/4(E_(0)^(2))/(mu_(0)c^(2))" " ( :. B_(0)=(E_(0))/c)`
`=1/4epsilon_(0)E_(0^(2)" "( :.c=1/(sqrt(mu_(0)epsilon_(0))))`
`=1/4xx8.854xx10^(-12)xx(2)^(2)=8.854`
`xx10^(-12)Jm^(-3)`
`~~8.86xx10^(-12)Jm^(-3)`