A plane electromagnetic wave of frequency `25 Mhz` travels in free space along the x-direction. At a particular point in space and time, `E= (6.3 j) V//m`. What is `B` at this point?

Options

A. `8.33xx10^(-8)hatkT`
B. `18.9xx10^(-8)hatkT`
C. `2.1xx10^(-8)hatkT`
D. `2.1xx10^(-8)hatiT`

Answer

C

Explanation

Here, `vecE=6.3hatjV//m`
The magnitude of `vecB` is `B=(E)/(c)=((6.3V//m))/((3xx10^(8)m//s))=2.1xx10^(-8)T`
`vecE` is along y - direction and the wave propagates along x - axis. Therefore, `vecB` should be in a direction perpendicular to both x - and y - axes. Using vector algebra `vecExxvecB` should be along x - direction.
Since `(+hatj)xx(+hatk)=hati, vecB` is along z - direction.
Thus, `vecB=2.1xx10^(-8)hatkT`