Question

The electric field of a certain plane electromagnetic wave is given by $E_x=0,E_y=0,E_z=2.0\cos \left[\pi \times 10^{15}\left(t-\frac{x}{c}\right)\right].$ The wave is propagating in the positive $x$-direction. Find the expressions for the components of the magnetic field of the wave.

• A. $B_x=0,B_y=6.7\times 10^{-9}\cos \left[\pi \times 10^{16}(t-x/c)\right],B_z=0$
• B. $B_x=0,B_y=-6.7\times 10^{-9}\cos \left[\pi \times 10^{15}(t-x/c)\right],B_z=0$
• C. $B_x=0,B_y=0,B_z=2.0\cos \left[\pi \times 10^{15}(t-x/c)\right]$
• D. $B_x=0,B_y=0,B_z=-6.7\times 10^{-9}\cos [\pi (t-x/c)]$

Answer 1

Answer: (B)

At plane, electromagnetic wave travelling with velocity $c=3\times 10^{8}m/s$ along $x$-axis, then electric field vector $E$ is along $y$-axis while the magnetic field vector is along $z$-axis $B_x=0$
$B_y=-\frac{E_z}{C}=\frac{2.0\cos \left[\pi \times 10^{15}(t-x/c)\right]}{3\times 10^8}$
$B_y=-6.7\times 10^{-9}\cos \left[\pi \times 10^{15}(t-x/c)\right]B_z=0$