We may view a [electric field](Electric%20field.md) and [magnetic flux density](Magnetic%20flux%20density.md), $\mathbf{E}$ and $\mathbf{B}$ respectively, as solutions to the [the wave equation](The%20Wave%20Equation.md). # Through a medium # In a vacuum This version of the wave equation is written in the following form for the [electric field](Electric%20field.md) as $\nabla^2\mathbf{E}(\mathbf{r},t)-\frac{n^2}{c^2}\partial_t^2\mathbf{E}(\mathbf{r},t)=0$ ^03e3b8 and $\nabla^2\mathbf{B}(\mathbf{r},t)-\frac{n^2}{c^2}\partial_t^2\mathbf{B}(\mathbf{r},t)=0$ for the [magnetic flux density](Magnetic%20flux%20density.md) where $n$ is the [index of refraction](Index%20of%20refraction.md), which we will take to be $n=1$ in a vacuum. # Solutions of the Electromagnetic wave equations The solutions of these wave equations are used to define the [light-field](Light-field.md) #Electromagnetism/Optics/waveOptics