Question

rules for geometrical construction for images in the case of concave lence?​

Answer 1

A lens has focal points F1 and F2 in front of and behind the lens, respectively. The focal length of a converging lens is positive f > 0. The object is in front of the lens so that we always have do > 0. If the image is behind (in front of) the lens, then di > 0 (di < 0)