Physics
Electromagnetic wave
E and B at right angles, in step, travelling at 1/sqrt(e0*m0) - the speed that made light an electromagnetic wave. Poynting points the way.
What happens
The speed is not a knob here. It comes out of the two constants of electrostatics and magnetostatics as 1/sqrt(e0*m0), and that number turning out to be the speed of light is the whole argument. Set the wavelength and the frequency follows; B is computed from E rather than drawn beside it, so the right angle between them is a consequence and not a decoration.
Equations used in the module
Equations E × B points along the travel, E = c B c = 1 / √(ε₀ μ₀) S = E × B / μ₀ (Poynting)
