Using the definition of the electromagnetic fields in terms of potentials, we then have the Fourier-form of the electric and magnetic field: E → → ( k → → , ω ω ) = i ( ω ω ε ε ( ω ω ) c v → → c − − k → → ) Φ Φ ( k → → , ω ω ) and B → → ( k → → , ω ω ) = i ε ε ( ω ω ) k → → × × v → → c Φ Φ ( k → → , ω ω )