There are similar rules for constructive ray-diagrams for obtaining image with concave lenses.
Rule 1. A ray of light which is parallel to the principal axis of a concave lens , appears to be coming from it's focus after Refraction through the lens.
Rule 2. A ray of light passing through the optical centre of a concave lens goes straight after passing through the lens.
Rule 3. A ray of light going towards the focus of a concave lens , becomes parallel to its principal axis after Refraction through the lens.
Formation of image by a concave lens :
1. When an object is placed anywhere between optical centre (C) and infinity in front of a concave lens , the image formed is :
(i) Between optical centre (C) and focus (F).
(ii) Virtual and Eract
(iii) Diminished ( Smaller than the object).
2. When an object is at Infinity from a concave lens , the image formed is :
(i) At focus (F).
(ii) Virtual and Eract
(iii) Highly diminished ( Much smaller than the object ).
