Question

Electric field and magnetic field of an electromagnetic wave propagating through a medium is given by, $E=E_{\circ }\sin (kx-\omega t)$ and $B=B_{\circ }\sin (kx-\omega t)$ respectively, then -

• A. $E_{\circ }k=B_{\circ }\omega$
• B. If the electric field is in $y-$direction, then the magnetic field should be in $z-$direction.
• C. The speed of the electromagnetic wave is $\frac{E_0}{B_0}$.
• D. All the above

Answer 1

The correct option is D All the above

Given:
$E=E_{\circ }\sin (kx-\omega t)$
$B=B_{\circ }\sin (kx-\omega t)$

We know that, speed of the electromagnetic wave is,

$c=\frac{E_0}{B_0}=\frac{\omega }{k}\Rightarrow$ Option $\left(C\right)$ is correct

$\Rightarrow E_{0}k=B_0\omega \Rightarrow$ Option $\left(A\right)$ is correct

Also, if the electric field is in $y-$direction, then the magnetic field should be in $z-$direction as both electric and magnetic fields are always perpendicular to each other during propagation of an electromagnetic wave.

$\Rightarrow$ Option $\left(B\right)$ is correct

As options $\left(A\right),\left(B\right)$ and $\left(C\right)$ are correct, hence, option $\left(D\right)$ is the correct answer.