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. `13.29 xx 10^(-12)`
B. `8.86 xx 10^(-12)`
C. `17.72 xx 10^(-12)`
D. `4.43 xx 10^(-12)`

Answer

B

Explanation

Amplitude of electric field and magnetic field and related by the relations , `(E_(0))/(B_(0)) = c`
Average energy density of the magnetic field is
`mu_(B) = (1)/(4) (B_(0)^(2))/(mu_(0)) = (1)/(4)(E_(0)^(2))/(mu_(0)c) , (":' B_(0) = (E_(0))/(c))`
`= 1/4 epsi_(0)E_(0)^(2) , (":' c = (1)/(sqrt(mu_(0)E_(0))))`
`= 1/4 xx 8.854 xx 10^(-12) xx 2^(2)`
`= 8.854 xx 10^(-12) Jm^(-3)`
`= 8.86 xx 10^(-12) Jm^(-3)`