Copy of Convergent lens
Convergent lenses deviates light rays running parallel to optical axis toward the lens focus. Rays passing through the center of the lens are not deviated. The image of an object is formed where the light rays starting from any point of it cross each other.
Move the object position F with respect to the lens and, in particular, closer or farther with respect to the focus. Try also changing the focus position. What happen to the image? Try to figure out how lenses are used in various devices (glasses, projectors, magnifying glasses, etc.).