Lens Power⚠ unverified
Physics / Optics · Compute the lens power in diopters from a focal length
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| P | P | m | 1.0 | Focal length |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | power | 1/m | Lens power, in diopters (1/m). Returns positive infinity when the focal length is zero |
The science & history
Understanding the Parameters
- $f$ — positive converging, negative diverging in the usual sign convention.
- Power — +2.5 D reading glasses correspond to $f = 0.4$ m.
Derivation (Approaching a Proof)
Definition: power is reciprocal focal length in metres, $P = 1/f$, so successive thin lenses in contact add powers: $P_{\mathrm{tot}} = \sum P_i$.
History
The dioptre is the optometry unit of lens power; power addition is standard ophthalmic optics.
Related Concepts: Lensmaker's Equation, Lens Magnification, Mirror Focal Length
Notes: Registry calculator lens-power (unverified). Naming bug: input labelled $P$ but is
focal length in m.