Thin Lens Equation Calculator
Image Distance from Focal Length & Object Distance
Focal Length from Object & Image Distance
Formula
1/f = 1/do + 1/di, where f is focal length, do is object distance, and di is image distance. Magnification M = -di/do.
Frequently Asked Questions
What is the thin lens equation?
The thin lens equation relates the focal length (f), object distance (do), and image distance (di) of a thin lens: 1/f = 1/do + 1/di. It applies to both converging and diverging lenses.
What is the sign convention?
By convention, distances are positive when measured in the direction of light propagation. Object distance is positive when the object is on the incoming side of the lens. Image distance is positive for real images (opposite side) and negative for virtual images (same side as the object). Focal length is positive for converging lenses and negative for diverging lenses.
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