# Angle between electric and magnetic field

1. Homework Statement
Hi. This is my first question on PF so please forgive me if something's not right

So I'm stuck at this question in EMT
In frame1, E and B are parallel and related by E=cB. We are required to find the cosine of the angle between electric field E' and magnetic field B' in another frame (The answer is to be in terms of B and B')

2. Homework Equations
We know that if E = Eo*e^(ik.r-wt) along n vector
then B = Bo*e^(ik.r-wt) along (n X k), where k is the wave propagation vector.and Bo = Eo/c

3. The Attempt at a Solution
Well I'm stuck at the first line itself. How can E and B be parallel? They're both always at 90 deg to each other as well as to the direction of propagation of the wave (as shown by the directions in the above two equations), isn't it?

## Answers and Replies

Orodruin
Staff Emeritus
Homework Helper
Gold Member
Is this the exact wording of the problem? It mentions nothing about a wave. Please always reproduce the problem statement exactly as given.

Is this the exact wording of the problem? It mentions nothing about a wave. Please always reproduce the problem statement exactly as given.

I am afraid this is the exact wording of the problem.

Orodruin
Staff Emeritus