Draw a ray diagram to show the formation of an image by a concave lens when the object is placed between F and 2F.

The ray diagram is shown below :

A ray from the top of the object travelling parallel to the principal axis, after refraction, appears to come from the focus F₁ on the same side of the lens, while a ray directed towards the optical centre O passes undeviated. These two refracted rays appear to meet at A'.

The image A'B' so formed is virtual, erect and diminished, and it lies between the optical centre and the focus F₁, on the same side of the lens as the object.