Lens-Maker's Equation

$$\frac{1}{F} = \left(n-1\right) * \left(\frac{1}{R_1} - \frac{1}{R_2}\right)$$

$$F = \frac{1}{\left(n-1\right) * \left(\frac{1}{R_1} - \frac{1}{R_2}\right)}$$