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Proof of Thin Lens Equation

The thin lens equation –– where

is the focal length

is the distance of the object from the lens

is the distance of the image from the lens

can be easily derived using properties of similar triangles.

The triangles CAB and CDE are similar, so(1)where O is the size of the object and I is the size of the image.

The triangles GBF and GFC are also similar so

Hence

From (1)hence

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