This to say that the radiated field cancels out the incident field and creates a transmitted field traveling within the medium at speed c/n. Using the same logic, outside the medium the radiated field produces the effect of a reflected field E R traveling at speed c in the opposite direction to the incident field. E r a d ( z , t ) = − − E v a c ( z , t ) − − E R ( z , t ) assume that the wavelength is much larger than the average separation of atoms so that the medium can be considered continuous. We use the usual macroscopic E and B fields and take the medium to be nonmagnetic and neutral so that Maxwell's equations read ∇ ∇ ⋅ ⋅ E = 0 ∇ ∇ ⋅ ⋅ B = 0 ∇ ∇ × × E = − − ∂ ∂ B ∂ ∂ t ∇ ∇ × × B = μ μ 0 J + ϵ ϵ 0 μ μ 0 ∂ ∂ E ∂ ∂ t both the total electric and magnetic fields E = E v a c + E r a d , B = B v a c + B r a d the set of Maxwell equations inside the dielectric ∇ ∇ ⋅ ⋅ E r a d = 0 ∇ ∇ ⋅ ⋅ B r a d = 0 ∇ ∇ × × E r a d = − − ∂ ∂ B r a d / ∂ ∂ t ∇ ∇ × × B r a d = μ μ 0 J + ϵ ϵ 0 μ μ 0 ∂ ∂ E r a d / ∂ ∂ t where J includes the true and polarization current induced in the material by the outside electric field. We assume a linear relationship between the current and the electric field, hence J = σ σ ( E v a c + E r a d )