Editing Refractive index (section)

===Lenses===
[[File:Lupa.na.encyklopedii.jpg|thumb|alt=A magnifying glass|The [[optical power|power]] of a [[magnifying glass]] is determined by the shape and refractive index of the lens.]]

The [[focal length]] of a [[lens (optics)|lens]] is determined by its refractive index {{mvar|n}} and the [[Radius of curvature (optics)|radii of curvature]] {{math|''R''{{sub|1}}}} and {{math|''R''{{sub|2}}}} of its surfaces. The power of a [[thin lens]] in air is given by the simplified version of the [[Lensmaker's formula]]:<ref>{{cite web |first=Carl R. |last=Nave |title=Lens-makers' formula |website=HyperPhysics |series=Department of Physics and Astronomy |publisher=Georgia State University |url=http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenmak.html |access-date=2014-09-08 |archive-url=https://web.archive.org/web/20140926153405/http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenmak.html |archive-date=2014-09-26}}</ref>
<math display="block">\frac{1}{f} = (n - 1)\left[\frac{1}{R_1} - \frac{1}{R_2}\right]\ ,</math>
where {{mvar|f}} is the focal length of the lens.