A plane `E.M.` wave of frequency `40 MHz` travels along `X`-axis. At same point at same instant, the electric field `E` has maximum value of `750 N//C` in `Y`- direction. The magnitude and direction of magnetic field is

Explanation

(i) Wavelength of the wave, `lambda = (c)/(v) = (3.0xx10^(8))/(40 xx 10^(6)) = 7.5 m`
(ii) Given, maximum value of electric field, `E_(0) = 750 NC^(-1)`
`:.` Magnetic field, `B_(0) = (E_(0))/(c) = (750)/(3xx10^(8)) = 2.5 xx 10^(-6) T`
Since `E` and `B` are mutally perpendicular and they both are perpendicular to the propagation of wave. Thus, we concluded that magnetic field is in negative z-direction.