A plane electromagentic wave of frequency 25 MHz travels in free space along the x-direction. At a particular point in space and time , E=6.3 `hatj` V/m . What is B at the point ?

Explanation

Using Eq. `B_(0)=[E_(0)//C]` the magnitude of B is
`B=(E)/(c)`
`=(6.3 V//m)/(3xx10^(8) m//s)=2.1xx10^(-8)T`
To find the direction , we not that E is along y-direction and the wave propagates along x-axis. Therefore, B should be in a direction perpendicular to both x-and y-axes.Using vector algebra, `E xx B` should be along x-direction . Since `(+hatj)xx(+hatk)=i`, B is along the z-direction . Thus, B=`2.1xx10^(-8) hat kT`