This equation calculates `alpha` (using `mu_1`, `mu_2`, `n_1`, and `n_2`), used in calculating the amplitudes of EM waves striking an interface. For more information and context on this equation, please see the EM waves at the interface of two insulators.
`mu_1` is the permeability of the first material
`mu_2` is the permeability of the second material
`n_1` is the speed of the wave in the first medium
`n_2` is the speed of the wave in the second medium