A plane electromagnetic wave of frequency 25GHz is propagating in...

Given, the electromagnetic wave is propagating in $z$ i.e., + \overset{^}{k} direction.

The relation between the magnitudes of electric field, magnetic field and the speed of light is given by

$\dfrac{\left|E\right|}{\left|B\right|} = C$

$⇒ \left|E\right| = \left|B\right| \times C$
$⇒ \left|E\right| = 5 \times {10}^{- 8} \times 3 \times {10}^{8} = 15V{m}^{- 1}$

We know that the direction of propagation of electromagnetic wave is along $\overset{\to}{E} \times \overset{\to}{B}$.

So, \overset{\to}{E} = 15\overset{^}{i}V{m}^{- 1}