Lensmaker's Equation

The Lensmaker's Equation is used to calculate the focal length of a lens immersed in a medium with an index of refraction of 1. The equation is:
`f=[(n-1)|1/r_1pm1/r_2|]^-1`, where:

• `n` = index of refraction
• `r_1` = radii of curvature
• `r_2` = radii of curvature

The positive sign is used when both surfaces are curved outward or both are curved inward; otherwise a negative sign applies. (In vCalc, enter `r_2` as negative if both surfaces are not curved in the same direction.)

References

31.3 The lensmaker's equation by Benjamin Crowell, Light and Matter  licensed under the Creative Commons Attribution-ShareAlike license.