Physics
Lens Formula
Relate focal length, image distance and object distance for a thin lens.
1/f = 1/v - 1/u
Formula Explanation
This is the Cartesian sign-convention form of the thin-lens formula.
Variables Explained
f = Focal length; v = Image distance; u = Object distance.
Solved Example
A thin lens has u = -30 cm and f = 15 cm. Find v.
1/v = 1/15 - 1/30 = 1/30; v = 30 cm.