Signals and Systems: Maxwell Equations and Light

And Maxwell said

$\large \mathbf{\nabla} \cdot \mathbf{D} = \rho\\ \nabla \cdot \mathbf{B} = 0\\ \nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}\\ \nabla \times \mathbf{H} = \mathbf{J}_ + \frac{\partial \mathbf{D}} {\partial t}$