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. (8.10), the magnitude of B is
`B =(E)/(C )`
`=(6.3V//m)/(3xx10^(8) m//s)=2.1xx10^(-8) T`
To find the direction, we note 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, `(+ hat j) xx (+ hat k ) = hat i` , B is along the z-direction. Thus, `B = 2.1 xx 10^(-8) hat k T`