PHYSICS / GEOMETRIC OPTICS
Calculate thin-lens focal length in air from refractive index and signed surface radii. See the governing equation, substituted values, result, assumptions, and interpretation in one guided workspace.
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Calculate thin-lens focal length in air from refractive index and signed surface radii. The page evaluates the displayed equation from your supplied values and presents both symbolic and substituted KaTeX working so the arithmetic can be checked.
1/f=(n-1)(1/R1-1/R2)
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What you receive
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The lens is thin, surrounded by air, paraxial, and radii follow the stated sign convention.
Use internally consistent units and retain extra precision when carrying the result into another calculation.
Reviewed reference factors