Substituting the sign convention we get. The lens equation expresses the quantitative relationship between the object distance do the image distance di and the focal length f. Dividing both the sides by uvf we get.
The derivation of the Gaussian form proceeds from triangle geometry.
Ii Where should an object be held from the lens so as to obtain a virtual image of magnification 2. This is the lens maker formula derivation. The focal length of a lens depends upon the refractive index of the material of the lens and the radii of curvatures of the two surfaces. A lens formula may be defined as the formula which gives the relationship between the distance.