Question 1 What are the sign conventions for measuring the distances for spherical lens?
Question 2 The image formed by concave lens is seen to be virtual, erect and highly diminished than the object. What is the position of the object?
Question 3 Where should an object be placed in front of a concave lens so as to obtain image between focus and optical centre?
Images formed by Concave Lens
Object is at infinity
(1) Image is formed at F1
(2) It is highly diminished, virtual and erect.
Object is between Infinity and Optical Centre of Lens
(1) Image is formed between focus and optical centre of the lens.
(2) It is virtual and erect.
Sign conventions for spherical Lenses
(1) All distances are measured from optical centre of a lens.
(2) Distances measured in direction of propagation of incident ray of light are taken as positive, while distances measured in a direction opposite to the direction of incident ray of incident are taken as negative.
(3) Upward heights wrt principal axis are taken as positive, downward height wrt to ray of light are taken as negative.