Electric & magnetic field vector help. E=Bc

[Joe626]

Homework Statement

At one instant, the electric and magnetic fields at one point of an electromagnetic wave are E = 300i + 50j − 200k V/m, and B = Bsub0 (1.7i − 3.9j + ak μT.

(a) What are the values of a and B0?
(b) What is the Poynting vector at this time and position?

Homework Equations

E = Bc
s = (E x B) / (mu sub0)

The Attempt at a Solution

i tried to find Bsub0 using the equation E = Bc for the i and j vectors but the answers are inconsistent. any help would be appreciated

 

[Spinnor]

You know E dot B = 0 that should give you the unknown a. See vector dot product,

http://en.wikipedia.org/wiki/Dot_product

And you know the magnitude of E is related to the magnitude of B, that relationship will give you B_o.

Good luck!