Question

The electric and the magnetic field, associated with an EM wave propagating along the $+z$ -axis, can be represented by

• A. $\left[\overset{ \rightarrow }{E } = E ⁡_{0} \hat{i ⁡},\overset{ \rightarrow }{B ⁡} = B ⁡_{0} \hat{j ⁡}\right]$
• B. $\left[\overset{ \rightarrow }{E } = E ⁡_{0} \hat{k ⁡},\overset{ \rightarrow }{B ⁡} = B ⁡_{0} \hat{i ⁡}\right]$
• C. $\left[\overset{ \rightarrow }{E } = E ⁡_{0} \hat{j ⁡},\overset{ \rightarrow }{B ⁡} = B ⁡_{0} \hat{i ⁡}\right]$
• D. $\left[\overset{ \rightarrow }{E } = E ⁡_{0} \hat{j ⁡},\overset{ \rightarrow }{B ⁡} = B ⁡_{0} \hat{k ⁡}\right]$

Answer 1

Answer: (A)

The electromagnetic wave is propagating along the +z axis.
Since the electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of propagation of wave.
$\text{Also,} \overset{ \rightarrow }{E } \times \overset{ \rightarrow }{B ⁡} $ gives the direction of wave propagation.
$\overset{ \rightarrow }{E }=E⁡_{0}\hat{i ⁡}\text{,}B=B⁡_{0}\hat{j ⁡}\left(\because \hat{i ⁡} \times \hat{j ⁡} = \hat{k}\right)$