I think the equation for the relationship of the E (electrical) and B (magnetic) fields in electromagnetic (EM) radiation is E=Bc, where c is the speed of light. I think this is correct, but what does it tell us? On it's face, it looks as though the B field (of a photon, say) is 1/300,000,000th the strength of the E field. Is this not correct? Why, then, do we see these diagrams of the EM propagation of say, light, where the proportion of the E and B field appear to be equal? According to that equation, the size of the B field would be almost negligible. So why am I seeing blue lines on this diagram? I've heard it both ways, though: 1) that the B field is, indeed, much smaller than than the E field in EM radiation, and 2) that they are actually the exact same in field strength. I can spend some valuable time searching for the references but it's going to cost you if you make me do that I think the counter-argument is that you can just set the speed of light to 1 and then the equation just becomes E=B? Its that simple? And perhaps this is the case because EM radiation is relativistic, and always travels at c so therefore we should set c to one here? Or is this bad logic? In any case, what is the answer? Are the strengths of the E and B fields identical in a traveling EM wave or is the E field much stronger than the B field?