Give the position, size and nature of image formed by a concave lens when the object is placed:
(a) anywhere between optical centre and infinity.
(b) at infinity.

(a) In the case of a concave lens, when an object is placed anywhere between the optical centre and infinity, the image is formed between the optical centre and the focus. The image formed is virtual, erect and diminished.

(b) In the case of a concave lens, when an object is placed at infinity, the image is formed at the focus. The image formed is virtual, erect and highly diminished.