- The potential difference between the plates $=\mathrm{V}$
$\scriptsize{ V=E_2 \times(d-t)+E_1 \times t}$
$\scriptsize{\mathrm{V}=\frac{\sigma}{\varepsilon_0} \times(d-t)+\frac{\sigma}{\varepsilon_0 K} \times t}$
$\scriptsize{\mathrm{V}=\frac{q}{A \varepsilon_0} \times\left[(d-t)+\frac{t}{K}\right]}$
$\mathrm{C}=\frac{q}{V}$
$C=\frac{\varepsilon_0 A}{(d-t)+\frac{t}{K}}$