An incident ray of light coming from the object parallel to the principal axis of a concave lens after refraction appears to come from its focus.
An incident ray of light passing through the optical centre comes out of the lens without any deviation.
A concave lens always gives a virtual, erect and diminished image whatever may be the position of the object. Let us now draw ray diagrams to show the position of the images when the object is placed - at infinity and between O and F1 and Any position between infinity and O.
When the Object is at Infinity
The image is:
formed at F1 erect virtual diminished
When the Object is placed at any Position between O and infinity
The image is:
formed between O and F1 erect virtual diminished
