Lens Maker's Equation (Sign Convention Form) (1/f = (n-1)(1/R₁ - 1/R₂))
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1/f = (n-1)(1/R₁ - 1/R₂)
What each symbol means
| Symbol | What it stands for |
|---|---|
| f | Focal length of the thin lens (m) |
| n | Refractive index of lens material relative to surrounding medium |
| R_1 | Radius of curvature of first surface (light hits first) |
| R_2 | Radius of curvature of second surface |
When to use this
Thin lens in air. Use Cartesian sign convention for R₁ and R₂. For biconvex: R₁>0, R₂<0. For biconcave: R₁<0, R₂>0. This entry focuses on NCERT sign-convention application and common R₁/R₂ sign errors.