# Electric Field and Magnetic Conversion

1. Jun 15, 2013

### onelastdance

In the solutions of a particular problem, it was stated that:

<P> = 1/2 |S| = 1/(2μ0) * E^2 / c

Where <P> is the average power, S is the Poynting vector.

From the above equation does that mean: B = E /(2μ0c) ?

I was just wondering how you can show the above relation between Magnetic and Electric field.

Last edited: Jun 15, 2013
2. Jun 15, 2013

### marcusl

No it doesn't. The Poynting vector is $$\mathbf S=\frac{1}{\mu_0} \mathbf E \times \mathbf B$$
and, for a wave propagating in free space, B and E are normal to each other (and to the direction of propagation) and have magnitude $B = \frac{1}{c} E$. Look it up. When you take a time average to get power, it devolves to your first expression.

Last edited: Jun 16, 2013
3. Jun 16, 2013

### onelastdance

Oh ok, thanks.

Last edited: Jun 16, 2013