Question

determine focal length of convex lens by two pin method

Answer 1

The focal length of a license in the air is the distance from the center of the lens to the principal foci or focal points of the convex lens.

For a converging lens which is called a convex lens, has a positive focal length, and is the distance at which a beam of acclimated light will be focused to a single spot.

To measure the focal length of a converging (convex) lens, use the formula: 1/u + 1/v = 1/f, the focal length f of the lens can be found.