\frac{E_{r 0}^{∥}}{E_{i 0}^{∥}} = \frac{E_{r 0}^{⊥}}{E_{i 0}^{⊥}} = \frac{n_{1} - n_{2}}{n_{1} + n_{2}}

${\frac{E_{r0}^\parallel}{E_{i0}^\parallel }=\frac{E_{r0}^\perp}{E_{i0}^\perp}=\frac{n_1 - n_2}{n_1+n_2}}$