### Shortcut Methods

##### 2 : Thin Lens Approximation

- For thin lenses (lenses with small thickness compared to their focal length), you can use the thin lens approximation: $$(\frac{1}{f} \approx (\mu - 1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)),$$ where μ is the refractive index and R
_{1}and R_{2}are the radii of curvature of the lens surfaces. - This simplifies calculations for thin lenses without needing the lens maker’s formula.