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Optics
Optics

Lensmaker's Equation

1f=(n−1)(1R1−1R2)\frac{1}{f} = (n-1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)

Relates the focal length of a lens to its refractive index and surface curvatures.

Variables

f
Focal length
m
n
Refractive index of lens
unitless
R_1
Radius of first surface
m
R_2
Radius of second surface
m

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Common questions

What is the Lensmaker's Equation formula?

Lensmaker's Equation is written 1/f = (n-1)(1/R₁ - 1/R₂). Relates the focal length of a lens to its refractive index and surface curvatures. It belongs to Optics, under Lenses.

What are the units in 1/f = (n-1)(1/R₁ - 1/R₂)?

In SI units, f is focal length, measured in m; n is refractive index of lens (dimensionless); R_1 is radius of first surface, measured in m; R_2 is radius of second surface, measured in m.