# Homework Help: Units of electromagnetic Wave

1. Feb 6, 2006

### dowjonez

B = k / w ( Z x E)

Check this equation by deriving the units for B

w = omega
Z = z hat

2. Feb 6, 2006

### scholzie

What have you done so far?

3. Feb 6, 2006

### dowjonez

k = 2pi / lamdba
w = 2 pi V / lamba

So B = 1/V ( Z X E)

B = 1/ [ m / s ] ( Z X E )

[E] = [q] / [E0] [ R^2]

[E] = [C] / [C^2/ Nm^2] [ m^2] = [N / C]

B = [s / m] * ( Z x [N / C])

4. Feb 6, 2006

### dowjonez

but = N / A * m

5. Feb 6, 2006

### scholzie

[C / s] = [A], so 1/[A] = [s / C]

[N] / [Am] = [N / m]*[1/A], right? so [N]/[Am] = [s/C]*[N/m], or [s/m]*[N/C]

I may have missed something, but I don't see a problem.

Also, be careful. V = voltage, v = velocity. It was hard to read your posts with some of those things in caps. This could have been easier if you noticed immediately that k/w = 1/v, which has units [s/m], and that E always has units [N/C]. Maybe you were expected to work it all out, but that's silly.

Last edited: Feb 6, 2006