Magnetic Field of Spherical Electromagnetic Wave

[Darly]

1. The problem statemeent, all variables and given/known data
The field electric's electromagnetic wave issued by a strut isotropic source is:

\vec{E} = E_{0} r_{0}*cos(ωt − kr) \vec{θ}

Find the magnetic field in spherical coordinates

Homework Equations

I think, i use the equation

 \vec{B} = \frac{1}{w} \vec{K} \times \vec{E}

But this equation use in planes waves, so for spherical waves too?
3. The Attempt at a Solution [/B]

 

[Simon Bridge]

\vec{E} = E_{0} r_{0}*cos(ωt − kr) \vec{θ}

Do you mean: $\vec{E} = E_{0} r_{0}\cos(\omega t − kr) \hat{θ}$ ?
note: you seem to have $\vec k\cdot\vec r = kr$

You want to know if the equation $\vec B = \frac{1}{w}\vec K \times \vec E$ holds for spherical waves?
I don't know what K and w stand for... but that equation does not look general to me.
You could always go back to Maxwell's equations to see.